There've been behind the scenes clashes as well. Multiple director changes, scripts thrown out and being rewritten, the entire tone and scope of the project supposedly changing after the initial plans for the DCEU fell apart. Allegedly, the major source of contention that led to Rick Famuyiwa's departure was that he signed on to make a more serious movie with some political undertones (supposedly touching on things like corruption and bigotry in the Central City Police Department where Barry works) and then the studio got cold feet and wanted something lighter when BVS underperformed. He wound up making a post dunking on WB when Black Panther did significantly better at the box office than Justice League, so it's clear there was no love lost there and that he didn't leave the film on the best of terms with the execs.
Then the Homecoming writers came onboard to do the lighter take WB wanted, but they apparently didn't get on well with Ezra Miller, and eventually departed (like Famuyiwa, they made a snarky post later implying that Ezra might be difficult to work with). Then we had Grant Morrison onboard to co-write a darker and more serious take with Ezra, but their script wound up being rejected by the studio.
Lots of false starts and pivoting of directions, basically.
