Quirks of the A3000.

[Matt_H]

Check your chip pairing. In case you haven't seen elsewhere, DMAC and Ramsey have to be used in specific pairs. DMAC-02 can only be used with Ramsey-04, and DMAC-04 can only be used with Ramsey-07. If you're using DMAC-02 with Ramsey-07, you're in uncharted, urecommended waters.

[Matt_H]

If that's the case, then I'm out of concrete ideas. Can you try another PSU?

I used to get random ramlib crashes on my 1200 when the 1260 accelerator had worked itself loose. How's the mounting of your Mercury?