No, I mean, with 5dim_transport + space-age, do you have two belts with a speed of 60 i/s? Then I regard it as a compatibility issue between them (unless there is a good reason to have two belts with the same speed).
Things like this can break LinkedBelts, as it skips belts that have the same speed as other belts, but doesn't check if the skipped belt is required for upgrades. So I think what happens is that linked-5d-underground-belt-04
is skipped as it would have the same speed as linked-turbo-underground-belt
which has already been added, but the linked-express-underground-belt
still upgrades to linked-5d-underground-belt-04
(because this is how the express underground belt upgrades with 5dim), which causes an error when Factorio checks the names at the end.