Ok so I did a total re-pot. Cleaned the rot away had a couple growing tips. I had to pot it sideways to keep all the pbulbs above the mix, as the way it was growing. Unfortunately the first leafless pbulb snapped off as I was removing the old mix..so I potted it up and put it in a plastic box...hope for the best. So bummed I hope the re-pot will stimulate some new growth. The old mix wasn't bad and no bugs. Also I put it in a smaller pot lots of styro in the bottom. Here are some pics.
Oncidiums have thin very numerous roots and sometimes these can hold moisture at the center of the rootmass and while you think the media is drying out, right there under the densest part, it is still wet. It looks like there is some coconut husk in there. That stays wet longer than bark. Also a porous bark will hold moisture under the center of the rootmass and cause rot. I would opt for a fan of some sort to make sure that there is some drying air around the oncidiums. Here is a pic of a wilsonara that I was sure was drying out but when I pulled it out of the pot, near the center under the rootmass it was still soggy. The outside of the rootmass was dry. So of course this little guy died. In the pic you see what was left as I tried to save it but when it started rotting it had 8 pbulbs. So check the center under the rootmass and make sure it is dry. This is also why I prefer the pot weight method of knowing when to water as opposed to the skewer method. Weight does not lie. Get some air on this plant and don't water at this time of year when it isn't actively growing. Only water it when it has new pbulbs that are growing roots. The new pbulbs aren't going to grow roots until around half grown or even later. You water and the plant isn't taking up the moisture. Oncidiums don't like to be wet. Moist is ok but not wet. True they don't like to be dry but a day or two dry is ok. During their dry season they go days with no water on their bare roots. Notice in the other pics how old the new pbulbs are when they start to get roots. They are at least halfway to maturity when they start to grow roots. Until then they are growing off the energy of the older pbulbs. Like a lot of orchids it has been recommended to allow a rest period and not water much at all until the new growth starts to put on roots. Good luck.