There is a very common problem with ft100/100d that caused a recall,
yaesu made a mess in peoples new radios & never fixed it after several failed attempts trying different stupid modifications,
ft100/d suffers from rf coupling into parts of the circuit that it should not,
often called the high vswr light issue, This could be your problem
yaesu tried to fix it with mickeymouse ground straps & copper foil on relays & bpf board,
I discovered what the real issue was when my 100d started acting up & have fixed a few for locals since then,
The coating on the upper & lower case is none conductive so they are not grounded,
yaesu used farty little strips of copper tape to create a capacitive coupling,
The tape on the sides does nothing at all, its not even contacting the chassis,
They also used the same farty little tape on the rear & middle of the cases where they touch the chassis,
That does work kind of but it gets dirty & loses contact with the chassis & the cases start coupling rf,
sometimes just cleaning the chassis & tape with stops the rf issues,
There is a much better fix that I posted on the ft100 user group years ago,
I pull the tape off & replace it with MUCH wider copper tape,
also run tape all along the sides of the cases so than when you put the screws back in the tape is contacting the raised bits of chassis where the screw go in,
That gives you coupling in multiple places umpteen times greater than stock,
it works on all bands.
Good luck I hope this is your issue because its a very easy fix.
