The Oav are always wrong ;) in the OVA of Janemba Vegeta is dead, Goku is alive Goten and Trunks are alive and know how to use the fusion and Gohan don't know the mystic form :) and Goku back to life after Gohan dead ;) so all the OAV is wrong :) because Are not produced by Akira Toriyama but by Toei Animation ;)

wait, i thought lord slug is between vegita's defeat and gohan's departure to namek?

but seriously, the movie's timeline is kinda confusing, i always wondered when did janemba event happen, goku's dead, same with vegeta

cooler's revenge, i know its problably when they wait 3-year for android, but gohan's hair is short there(same when namek saga)

It couldn't be after Vegea's defeat because Goku was in the hospital when they left for namek.

Don't try to place the movies in the series timeline, it's virtually impossible to do so with most of them, Lord Slug included. Just try to enjoy them as little alternative universes.