It seems to be the same launcher, Launcherv2, in all cases. Find a different launcher .apk file (search android launcher apk in Google), download it and copy it to the projector. Then find it in the projector (there must be a file manager app of some kind) and tap it. It should install or give you the choice of apps to use to install it. (You'll also get a notice that something has to be allowed - the wording changes depending on the version of Android - so follow the instructions and allow it. Then tap the launcher again and it will install. Tap the Home button and you'll be asked which launcher to use - choose the new one. If that also stops when you enable wifi, there's something seriously wrong with the software design of those projectors. If it works, there's something wrong with "Launcherv2". (Most launchers are available somewhere online - but there's not a single Google hit on "launcherv2", so it must be something they wrote themselves.)
In either case, the manufacturers should be contacted, as B. Diddy suggested. Properly written apps don't stop until you stop them, and Android devices access the internet.