It's a high resistance [bad] neutral.
If the saw is running on 100v the other side of the neutral is getting 240-100 = 140v and there is 20v across a connection that is supposed to have only a few mV across it.
With some appliances turned on [toasters and the like] put your voltmeter across the bolted neutral in the panel to see if that's where the problem is. If you short anything there is an arc-flash danger. Don't turn on incand. bulbs or expensive electronic stuff.
The bad connection may be hot and may make frying noises.
If the problem is upstream of this bolted connection you need to involve PoCo.