Has anyone ever reported a concern to the GPhC?

[Pharmacistquestion]

I have some concerns about a pharmacist colleague of mine.
Issues have previously been raised to their manger by myself, and 3 other members of staff that I am aware of. Nothing appears to have been done about it, as some of the issues were raised around 8-9 months ago prior to colleagues going on maternity leave.
Some of the issues I would consider serious, and I'm not sure if they need reporting to the GPhC. I'm going to discuss with my union and see what they say but I wanted some views if possible.