OK. The pump and fan will certainly be inductive so it could be worth just temporarily disconnecting these from the relay module to see if it has any impact on the problem.
The relay module can be powered powered by 2 different supplies. Vcc and JD-Vcc are separate. See the schematic in this link: 4 Channel 5V Relay Module - Wiki.
Incidentally, I've never previously seen a level shifter with a built-in regulator. I suppose it could be useful if you are connecting a 3.3 volt peripheral to a 5 volt Arduino (which you are not doing).