Relay vibrates off

The PB gas boiler manual says my DE-03-SV-WPC boiler should have a Honeywell R4222A1001 relay. The original went bad, so my plumber replaced it with a ZC90340 relay which vibrates loose over time, in spite of his efforts to tie it in place. When it gets too loose, the boiler won't shut off until I push it back into position. The poor man has since died, so I obviously can't call him back. Did he use the wrong replacement part? If so, what part do I need? It looks simple enough to just swap in a new one. I looked up the part number on the internet, and found the R4222A1001 was replaced with R4222B1082, but pictures of that relay show 4 prongs on the side where mine appears to only have 3 slots.