Chuck I am sitting here on the side but this has happened before.
1. The uBitx as it comes from factory, (you may have a Bitx40 you are not specific) is supposed to be biased correctly and the bias
instructions are supposed to be for set up a new pair of Mosfets. HOWEVER it would only take someone at the factory to be asleep and you could be where you are.
2. There have been a vast number of IRF510 mafrs over years and they are not all born equal. If you bought second tier components you may still have issues.
3. (the most useful one - possible GET OUT OF Jail ) . There are or used to be (Ashar Farhan does not ring me up to tell me every PCB rev) a number of top to bottom vias on the PCB around the IRFs. If you look front to back and against the schema you will pick em up. Some are carring a lot of RF. These have a rather sensitive plated through hole. Clearly it is hard to test them with a DVM unless you have a known good PCB along side - ie a reading non Zero on ohms may still be acceptable. However if fully toasted then putting through a bit of say Cat5e wire or a component lead and soldering both sides may just may get you out of jail. BUT at 30 Mhz the impedance of the fix will not be the same as a thin Cu PCB layer so you still may have a Princess board.