Noob here, so be gentle.
Using a 12v-5/3.3v power board, NodeMCU powers relay fine, 100% of the time. Add in the solenoid by soldering a line from the wall wart into the COM spot on the relay, and then 10-15% of the time, the activation of the solenoid resets the NodeMCU. Common ground for all of them obviously.
It should be possible to run them all, yes? But what do I need to add into the chain to keep the reset from happening? A capacitor? Magic? Help.