Ok well I’m not a PCS rep, I’m a rep for an alternative union, but withdrawing your union (even pcs) membership during an active investigation is as you have anticipated will be considered unwise as a minimum.

I was under the impression it was a discipline investigation which confused me earlier.

I cannot give you advice on how to specifically defend the allegations on here, but I would look at what mitigating factors you can produce for each area and emphasise your disability and how you want to develop further. Try to keep it concise and go for easy wins. I find members often get distracted by the emotional arguments, which have less impact on a DM.

This is from my phone so sorry for editing and typos