I had problems with power-on button. Temporary solution is very simple, so you may repair your radio and easily look for more time to replace original switch.
After you take out both upper, and bottom covers, you may unscrew upper display panel holding screws, and slightly loosen lower ones. Your display will fold toward you, so PCB will get accessible. At the left side toward you, there is power switch to be patched with two small
pieces of wire. (another pair of contacts is not used by Yaesu, so we
may use it here.