Replace the RAM with ECC ones (if the motherboard will support it). Or first, just try to take them out clean them with some alcohol and put them back, sometimes the contacts are getting rusted.

But anyways, for a full node I will recommend ECC RAM, especially for a LN node.

Another cause for SIGBUS error is the power supply. Cannot give the right voltage to the RAM and this is failing. If you can get an extra power source to test will be great.

SIGBUS comes from "segmentation bus". Is something wrong on your memory bus.

So yeah I will start in small steps: