Short version is don't use tugs; they're a pain in the ass and quite fiddly with order-of-operations.
I love tugs, especially now that we can build cheaper space stations with the "No Armour" checkbox.
I build a lot of mining platforms.
They don't move more often than every 20 years.
I'd much rather fiddle with tugs than pay for engines on each station.
The only thing to be wary of is that using the "Detach" button for a tractored ship causes problems.
Instead, you need to give the fleet the "Release tractored ships" order at your desired destination.