Your problem is probably either bad dram on dspA or a weak dspA processor. Because dspA also has the sampler ram, this places extra load on the memory bus, so it is more inclined to show problems.
But, all these parts are pretty much obsolete, and have not been available from reliable sources for many years, so there is little that can be done. If you had someone remove the 3 sampler dram chips, that might well fix it, but you would lose the sampler. And, alas, no guarantee.