ballast yes. its not firing properly causing your strobing, and with the old style bulb it wasnt firing enough to mix the gases. Might get into the guts so you can find the model you need.

Okay, thanks for your reply.

I've decided to jury rig a 4 foot LED shop light for now to get some light in the bathroom. I have a pair of 4' T8 tubes on order that will fit this fixture and can be direct connected to the incoming 115 V current. This will eliminate ballest problems on this fixture once and for all.

At least that's what I hope will happen. Fingers crossed.

by passing the ballest? that will send to much to the bulb. blow out.

LED Tubes won't blow out if they're specifically made for operation with no balast and direct connected to 115 volts. These are the type tubes I have on order. There is a youtube video online showing how to do this conversion.