Even though I'm still juniorish, I still run into issues like this that stump me. But then occasionally you do find bugs with existing software which keeps you second guessing everything. Usually those bugs come from using two things in conjunction that haven't been well tested together.
Also sometimes, you find a bug that isn't accepted by the software vendor/owning team as a bug, because it has some sort of obscure work around that would take you a week of tinkering to figure out. Those "aren't bugs" but yeah, they are bugs. Software vendors that also sell consulting and related services love to pull shit like that