I've been using Ultimaker about five years, Ultimaker 2 since 2014. The printers have given me a fairly easy ride I think though, as despite heavy use I only found the need to replace a part very recently. The failed part was the main board, and having installed the new main board from Ultimaker today, I powered up, and noticed a strange behaviour during bed levelling. Levelled the bed anyway, and attempted a first print with the new board. The video shows what happened :
The issue shown here is more or less the same as happened during the initial bed levelling. It happens each time the machine tries to start a print. After the collision, the bed lowers as shown, and proceeds to print some distance above the print bed. Re-levelling the bed makes no difference, as the gap reappears following the collision at the start of any print.
It's probably something obvious? I hope so!