I have seen this with one or 2 games on the 350, but its interesting that it does it all games on the 280v. I'll have need to have a look at the frame timing code. i suspect its skipping frames when it does not need to.
Interesting development. The Stock-Based Rogue firmware for RG280V was just updated to v1.7.10u7 which, seemingly accidentally, fixes this speed problem in Tac08. Carts now run at the proper speed while using this firmware.