HP colour printers, not working (Barnes SW13)

HP Color Laserjet 3800 and 3600n, both defective. The 3800 cassette door doesn’t close fully on the right hand side. I think part of the catch mechanism has broken. Before this the printer worked well for many years. The 3600n takes about 20 minutes to configure itself every time the printer is turned on. When it does print, it leaves a broad faint black stripe down the paper. However the cassette door closes fully. The printers look identical, so it may be possible for a competent technician to use a part from the 3600N to repair the 3800, or vice versa. There is only one fuser unit, working, which fits both printers. Both printers have part-used cartridges. Collection from SW13