USB serial appears in OS but doesn't respond to anything on ECP5/Orangecrab

[LithosphereRocketry]

I'm trying to run this code on an Orangecrab-25F (ECP5 core). I've made a few modifications to the example code to get it compatible with my setup, but nothing really significant: I am getting the 48MHz clock natively instead of from a PLL, and I removed the PipeSpec layer from the ECP5 interface because it seems to depend on some other piece of Verilog which I don't have in my setup. Here are my top-level file as well as the modified ECP5 interface:
Top level:

module orangecrab_core(
        input clk48,
        
        inout usb_d_p,
        inout usb_d_n,
        output usb_pullup,

        output rst_n,
        input usr_btn,

        output rgb_led0_r,
        output rgb_led0_g,
        output rgb_led0_b
        
    );

    orangecrab_reset reset_instance(
		.clk(clk48),
		.do_reset(~usr_btn),
		.nreset_out(rst_n)
	);


    // Generate reset signal
    reg [5:0] reset_cnt = 0;
    wire usb_rst = ~reset_cnt[5];
    always @(posedge clk48)
        reset_cnt <= reset_cnt + usb_rst;

    wire [7:0] uart_d;
    wire uart_ready;
    wire uart_valid;

    usb_uart uart(
        .clk_48mhz(clk48),
        .reset(usb_rst),

        .pin_usb_n(usb_d_n),
        .pin_usb_p(usb_d_p),

        // uart pipeline in
        .uart_in_data( uart_d ),
        .uart_in_valid( uart_valid ),
        .uart_in_ready( uart_ready ),

        .uart_out_data( uart_d ),
        .uart_out_valid( uart_valid ),
        .uart_out_ready( uart_ready )
    );
    assign usb_pullup = 1'b1;
    assign rgb_led0_r = 1'b1;
    assign rgb_led0_g = ~uart_valid;
    assign rgb_led0_b = 1'b1;

endmodule

Modified ECP5 layer:

module usb_uart (
  input  clk_48mhz,
  input reset,

  // USB pins
  inout  pin_usb_p,
  inout  pin_usb_n,

  // uart pipeline in (out of the device, into the host)
  input [7:0] uart_in_data,
  input       uart_in_valid,
  output      uart_in_ready,

  // uart pipeline out (into the device, out of the host)
  output [7:0] uart_out_data,
  output       uart_out_valid,
  input        uart_out_ready,

  output [11:0] debug
);

    wire usb_p_tx;
    wire usb_n_tx;
    wire usb_p_rx;
    wire usb_n_rx;
    wire usb_tx_en;

    // wire [11:0] debug_dum;

    usb_uart_core uart (
        .clk_48mhz  (clk_48mhz),
        .reset      (reset),

        // pins - these must be connected properly to the outside world.  See below.
        .usb_p_tx(usb_p_tx),
        .usb_n_tx(usb_n_tx),
        .usb_p_rx(usb_p_rx),
        .usb_n_rx(usb_n_rx),
        .usb_tx_en(usb_tx_en),

        // uart pipeline in
        .uart_in_data( uart_in_data ),
        .uart_in_valid( uart_in_valid ),
        .uart_in_ready( uart_in_ready ),

        // uart pipeline out
        .uart_out_data( uart_out_data ),
        .uart_out_valid( uart_out_valid ),
        .uart_out_ready( uart_out_ready ),

        .debug( debug )
    );

    wire usb_p_in;
    wire usb_n_in;

    assign usb_p_rx = usb_tx_en ? 1'b1 : usb_p_in;
    assign usb_n_rx = usb_tx_en ? 1'b0 : usb_n_in;

	// T = TRISTATE (not transmit)
	BB io_p( .I( usb_p_tx ), .T( !usb_tx_en ), .O( usb_p_in ), .B( pin_usb_p ) );
	BB io_n( .I( usb_n_tx ), .T( !usb_tx_en ), .O( usb_n_in ), .B( pin_usb_n ) );

endmodule

When I run this code, the device appears on my (Ubuntu 22.04) system as a device under lsusb and also appears as /dev/ttyACM0 as it should; however, any attempt to interact with it (via a terminal program or directly) crashes with an I/O error after about 10 seconds. Upon plugging it in, I see a bunch of concerning stuff in dmesg:

[ 3297.766279] usb 1-5: new full-speed USB device number 24 using xhci_hcd
[ 3297.923093] usb 1-5: New USB device found, idVendor=1209, idProduct=5af0, bcdDevice= 1.01
[ 3297.923110] usb 1-5: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 3297.923116] usb 1-5: Product: OrangeCrab r0.2 DFU Bootloader v3.1
[ 3297.923121] usb 1-5: Manufacturer: GsD
[ 3319.011295] usb 1-5: USB disconnect, device number 24
[ 3319.337786] usb 1-5: new full-speed USB device number 25 using xhci_hcd
[ 3319.486432] usb 1-5: New USB device found, idVendor=1d50, idProduct=6130, bcdDevice= 0.00
[ 3319.486447] usb 1-5: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 3319.489034] cdc_acm 1-5:1.0: ttyACM0: USB ACM device
[ 3336.197566] usb 1-5: reset full-speed USB device number 25 using xhci_hcd
[ 3336.325363] usb 1-5: device descriptor read/64, error -71
[ 3336.561351] usb 1-5: device descriptor read/64, error -71
[ 3336.797376] usb 1-5: reset full-speed USB device number 25 using xhci_hcd
[ 3336.925507] usb 1-5: device descriptor read/64, error -71
[ 3337.161369] usb 1-5: device descriptor read/64, error -71
[ 3337.397446] usb 1-5: reset full-speed USB device number 25 using xhci_hcd
[ 3337.397630] usb 1-5: Device not responding to setup address.
[ 3337.605588] usb 1-5: Device not responding to setup address.
[ 3337.813253] usb 1-5: device not accepting address 25, error -71
[ 3337.941240] usb 1-5: reset full-speed USB device number 25 using xhci_hcd
[ 3337.941342] usb 1-5: Device not responding to setup address.
[ 3338.149329] usb 1-5: Device not responding to setup address.
[ 3338.357223] usb 1-5: device not accepting address 25, error -71
[ 3338.357296] usb 1-5: USB disconnect, device number 25
[ 3338.485226] usb 1-5: new full-speed USB device number 26 using xhci_hcd
[ 3338.613232] usb 1-5: device descriptor read/64, error -71
[ 3338.857233] usb 1-5: device descriptor read/64, error -71
[ 3339.101325] usb 1-5: new full-speed USB device number 27 using xhci_hcd
[ 3339.233362] usb 1-5: device descriptor read/64, error -71
[ 3339.469269] usb 1-5: device descriptor read/64, error -71
[ 3339.577385] usb usb1-port5: attempt power cycle
[ 3339.993290] usb 1-5: new full-speed USB device number 28 using xhci_hcd
[ 3339.993472] usb 1-5: Device not responding to setup address.
[ 3340.201437] usb 1-5: Device not responding to setup address.
[ 3340.413279] usb 1-5: device not accepting address 28, error -71
[ 3340.549274] usb 1-5: new full-speed USB device number 29 using xhci_hcd
[ 3340.549444] usb 1-5: Device not responding to setup address.
[ 3340.757405] usb 1-5: Device not responding to setup address.
[ 3340.965239] usb 1-5: device not accepting address 29, error -71
[ 3340.965366] usb usb1-port5: unable to enumerate USB device
[ 3634.454077] usb 1-5: new full-speed USB device number 30 using xhci_hcd
[ 3634.606991] usb 1-5: New USB device found, idVendor=1d50, idProduct=6130, bcdDevice= 0.00
[ 3634.607006] usb 1-5: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 3634.609605] cdc_acm 1-5:1.0: ttyACM0: USB ACM device

Are there any known fixes for this type of issue?