This is most likely indicating a problem with the RAM added by your expansion card.
You can usually diagnose these problems better by booting with a diagnostics floppy. I would recommend trying the Amiga Test Kit v1.4.
It includes a boot floppy that runs a suite of tests, including a memory test that will probably recognize your additional RAM and can perform extensive tests. This will confirm that the RAM SIMM (vice the expansion card) is the likely culprit.
NOTE: As mentioned in the comments, C12 does look suspicious in your photo. If the memory test indicates intermittent problems with both SIMMs, or with a known good SIMM tested elsewhere, then recapping the expansion board may be your best bet.