Have windows on bottom deck and top front which have roller handles, i.e. they do not slide. Top deck has slides on sides, I guess because it was a tour bus, and the top comes off.

The bottom rollers work well.

The top deck in front go down OK, but try to close them and the handles mostly just spin, with a click each turn, and it sometimes takes two of us pulling up on he glass while turning the crank, to get the window to close.

Both top front suffer from this problem. Any hints on what might be wrong, and how I might get these working?

Thanks in advance.

My bus number (if any): RCL2259,

Take them out and clean them.
Take out the bottom two screws in the slides on both sides, drop the small catch at the bottom of the slide, wind the window down as far as it will go, remove top two screws both sides. Prise out slides and top half in one piece. Clean the cogwheels thoroughly on the bottom half, and the teeth inside the top half, get all the gunk out! Wind window handle to check the cogs turn. Put in grease through the handle nipple - reassemble.

My bus number (if any): RTL 960 RMC 1458, RM 1585 and loads of RTs

You may also find the bottoms of the straight cogs bits are badly worn, it's a common fault on most buses as the front windows tend to get wound up and down more than the others. You may have to replace these with parts from spare side windows.

My bus number (if any): RML2532