This is also my experience with GitLab CI.
It’s great if you have relatively simple CI. If you have anything slightly more complicated (like multiple child pipelines for a monorepo) you’re going to have a rough time.
Every time I thought I understood GitLab CI, it would fail/behave in non-obvious ways.
No matter what I did, every time I touched our CI pipeline code I could be sure to run into yet another Gitlab bug.