Yes, I think something related to all the testing and off/on cycles have upset one of the boards. I have several MB-8433UUD boards. The PCB revision numbers do not always agree with which PCB changes have been made to the board though. My inventory of this board is as follows,
MB-8433UUD v1 - 1 unit
(no version marking, so presumably version 1.0)
This board needs to have the PCI bus frequency reduced irregardless of the set frequency. For example, I need to set FSB-to-PCI multiplier at 2/3 or 1/2, even if using a 33 MHz FSB. As such, this board is defective.
MB-8433UUD v2 - 2 units
I have two of these. One has chipsets with 9622 datecodes, the other with 9534 datecodes. Even though both are version 2.0, the one with earlier datecodes clearly has some slight changes to the PCB. The earlier version 2.0 board has chipsets which are even older than those found on my version 1.0 board. I have not extensively tested the earlier v2.0 board because the chipsets are quite old in comparison. It is the later v2.0 board I have which no longer functions with Cyrix/IBM 5x86 CPUs. This board is now defective, however it is a good board to use with the Am5x86-160 or POD100 provided that you use 256 KB of double-banked cache. If you increase the cach to 512 KB, you can no longer use the fastest cache timings. In fact, you need to use the slowest cache timings.
MB-8433UUD v3 - 2 units
One version 3 board came stock with a socketed RTC, the other board had the RTC soldered on. One of these boards is being used as my IBM 5x86-133/2x system. It works well with my 1024K cache modification on a 66 MHz FSB. The other version 3 board I noted as possibly unreliable, but I am using it now for testing and it seems OK thus far.
MB-8433UUD v3.1 - 1 unit
I used this board for years without fail in a 24/7 server. Then one day the diskette controller (Super I/O chip) stopped functioning. I can put in an ISA diskette controller card, which worked with Win9x and DOS, however NT4 does not appreciate its presence and has issues with diskette access. I eventually need to cut off the old super i/o QFP chip and replace it. I have the replacement chips on hand, but no opportunity to replace it.
So I have 6 boards on hand, but only 2 seems fully functional. These boards were practically given away on eBay back in 2001.