I’ve been there OP and I didn’t agree with the informal PIP but we still went through the process. The workload was insane, I was doing around 2 hours a day unpaid overtime just to get through the workload.
I was put on an informal PIP and we had weekly meetings. First meeting I was told I hadn’t done ABC, made sure for the next week I nailed ABC, had the next meeting, I wasn’t doing DEF enough, ABC wasn’t mentioned. So for the next week I nailed ABCDEF, the next week meeting I wasn’t doing GHI well enough, no mention of ABCDEF. Killing myself to make sure I covered everything while they piled even more work on me. Even if I did 5 hours a day overtime I couldn’t keep up.
At the final meeting it went like this
them - you are still behind with your workload so we are going on a formal pip
me - don’t bother, here’s my resignation stick your job up your arse then walked out.
i had another job lined up and found out that most staff left or were managed out after 2 years, their staff turnover was horrendous.
start looking for another job, if they want you out they will get you out.