Yamaha R700 Distortion and Oscillation Trouble

[Benji01]

Hey Guys,
well the Yamaha R700 is back. Last time I repaired the tuner and replaced the output STK modules.
The receiver worked for couple of weeks than it stopped working. After opening the receiver it was quiete obvious what went wrong this time. Both STK modules died and some resistors burned.
After opening the broken STK Modules it was clear that the output transistors failed. They failed probably because they where cheap knock-offs. The transistor dies are smaller than the original and the modules are missing both emitter resistors.
So after a bit of research it was clear that I can't get any quality replacements for the STK1050II, so I found this thread on DiyAudio:
https://www.diyaudio.com/community/threads/stk1080ii-devices.332605/
So I decided to give the discrete version a try.
Well the discrete modules work but they have a couple of small problems.
If I use the R1/R2 as shown in the drawing and I want to set the quiescent current of the output transistors than the amplifier starts to oscillate at around 500kHz picture 12/13. If I replace R1/R2 with a 10K potentiometer and a 500Ohm resistor I can set the quiescent current without the oscillation.
Now to the other problem. As seen on picture 10 and 11 there is crossover distortion and I can't get rid of it no matter of how I set the quiescent current.
All transistors are with their gain more or less close to each other.
Does anyone here has an idea of what I can do to reduce or get rid of the crossover distortion ?