FTDI issue

Any one seen this occur?
I have an FTDI FT232 module, MIKROE483 from Mouser,
https://www.mouser.com/ProductDetail/Mikroe/MIKROE-483?

I have two of them soldered on a board with a '1284P chip.
When I plug in a USB cable, one does the Windows boop-boop and shows up as a COM port.
The other one also boop-boops, but then Windows puts up a Bad USB device messaage.
It looks like I'm stuck unsoldering the module, which will not be too easy.

The "bad USB" message is generally a really bad sign.

You aren't by any chance using the "standard" FTDI pinout on what you connected them to, are you?

Those don;t have the usual pinout - they have the pin order for CTS, RTS, and Vcc switched around... and a typical pinout board soldered to one of those will have Vcc shorted to ground (CTS is usually grounded on the microcontroller board)...

I have two boards built up. One connects ok, the other does not.
When I change the IO jumper to 3.3V, it connects up ok, but will not do Serial Download with a freshly bootloaded chip on the board (and I bootloaded it on the board). Changing the IO jumper to 5V and I get the Bad Device message, and in Device Manager something like request device descriptor failed shows up under USB Controllers.

The 1284P works in the system normally otherwise.

Other connections are SPI to 6 MAX7219s, SPI to two TPIC6B595s, 4x4 button array, and a transistor to drive an LED lamp (offboard). That all works fine. I pulled the chip and downloaded the code in a ZIF socket adapter I built up, put it in the board, and confirmed everything else is working.

It's just the FT232 that goes to Serial for downloads that is not working.

Got a help message in with Mikroelectronica. I've got 20 of these devices, wondering if I need to go thru and test them all. At the same time, I don't know if they'll fail without being installed in a system. There is no load on the 3.3V line, it just goes to the IO pin on the module.

Connections to the module are Rx, Tx, 5V, DTR, and the 2 LEDs for Tx & Rx. 5V lines are diode protected, and PTC fuse limited.
This is not the first time I've used this setup.
And as I said, one board works and one does not. We've been looking for anything we could find with a magnifying glass, checked the 5V coming out of the board. Can't really check the serial lines as Windows won't talk to the chip.

I'm out of ideas.

Maybe take the jumper off the suspect device and check the current between the middle pin of that jumper set and its 3v pin. Do a comparative test on the working board.
If that indicates an issue, maybe unsolder D3 from your own board and try again.

Think I found the issue. This is the bottom of the IO voltage select jumper. From the factory. Wasn't looking at the bottom when I installed pins. Will be checking the rest of my order now.

A 2nd board was found with 5V shorted to the middle pin.
2 out of 20 with a problem.

Is p2 soldered ?