The board will not function correctly without the RAM upgrade as it is missing 4 key parts which are instead placed on the upgrade board, per H3nry's observation. Since it exhibits the exact same symptoms in two different Macs, but also with or without the RAM upgrade, my guess is that this is something to do with the upgrade. I say this because the board without the upgrade exhibits the same symptoms as with, which suggests that this is default behavior without the 4 components missing from the board. Since it exhibits the same problem with the upgrade board, it appears the upgrade board is not functioning properly, if at all. Check to make sure the connections are all being made properly, and are tight and secure. Possibly clean all the contact pins looking for corrosion.

Of course it is possible there is another problem, separately or in addition to this one, causing the issue you are seeing, but the fact it persists both with and without the upgrade board suggests the problem is on the upgrade board ... To me anyway ... Definitely worth a thorough check.