Dynamic between Sandra vs the rest

In the early episodes there were some personality conflicts, differences of opinion and policing methods, plus the sometimes awkward status of Sandra being the only one on the team who is a serving police officer with the authority and responsibility. There was also the problem that only Jack and Sandra had worked together before - the impression being that Jack knew about Gerry and Brian without having actually worked with either one of them.

As each team member has their own special weak spots that can interfere with the job, there were later episodes where annoyance was appropriate, but they also developed a way of insulting each other with friendly banter - the team is like a family, but one that doesn't always agree about everything the family is doing.

Not knowing which episodes or events you're referring to makes it hard to know if it is animosity or comments made in a more friendly manner.

There is also the sense, at least for me, that Dennis Waterman eventually lost most of Gerry's charm, eventually becoming a grumpy, whining member of the team (still effective, but often annoying.) I still enjoyed the character, even though it seemed to take away from the unity of the team (personal opinion.)

Hopefully you will have an opportunity to see earlier episodes which would likely explain a lot of what's going on in season 8. Plus earlier episodes are often a bit more quirky (no one takes UCOS serious early on.)