Quickstep laminate - issue with closing piece

It's probably not the right thing to do, but a bead of glue under with something heavy on top? Then skirting board fitted tight over to stop it popping back up in time.

You sure the final piece is properly clicked in? I seem to remember having problems with a narrow final piece getting the leverage to click it fully in.

Once it's properly clicked it should lie flat without any additional help.

Yeah, echoing the 'it's just not quite clicked in all the way along' advice (or diagnosis anyway!). The tongue and groove is precision machined with a very tight tolerance so if it is isn't all sitting in place it won't sit properly. The pull tool is definitely your friend here, and the hammering can really help with shocking the pieces together.

Mmmmm. Not sure what to say - it's been a few years, but I did our entire ground floor way back with Quikstep: sometimes I got that same kind of issue on a last board, but it was always just not in properly somewhere: a tap with the puller tool would finally make it click into place.
Do any of the grooves perhaps have an imperfection or some grit in them?

Good luck

You sure the short join is properly seated as well. Sometimes you need to join all the final run together first. Before clicking it in place as one big piece.