LPT: If HR/management pull you in for performance measures/disciplinary action, always request figures in writing in advance and crosscheck them yourself. Don't assume HR have it right, and don't assume they will help you.

The two times that I've had Human Resources try to give me 'performance measures' or disciplinary procedures, I've checked the numbers they were using independently and found them to be so erroneous that the case against me was immediately dropped.

Even if the discrepancy is a small one, the fact that there is an error at all will go massively in your favour, as they should be triple checking anything they use against an employee in a disciplinary matter. My specific example involves shift cancellations/sickness, for context. If you have union access, then use it!

Don't assume Hr have things correct and definitely don't assume they are there to help you.