I worked for many years with a variant of RPTV units, and there is “always” a way to access the screen, either by sliding the framework holding the screen elements away from the cabinet or removing the electronics chassis from the cabinet. There may be other “ways in,” but I wouldn’t recommend one that changes the mirror’s alignment.

You may find some help from your manufacturer’s online or telephone tech support. When you start, just go slowly and carefully. Probably best to have another set of careful hands working with you.

If you can manage access that allows a vacuum cleaner hose inside without totally removing the screen, you might try that. If you are going to put a brush attachment on the end, make sure it’s really clean and dry. Sometimes one or more of the screen elements is a very finely textured Fresnel and/or diffusion lens. It’s good not to get dirt or finger oils into the grooves or texture. If you don’t use a soft brush, don’t “aim” the hose directly at the lens in order to prevent the lens suddenly being sucked to the hard plastic and being scratched.

If you remove most of the offending web, but the screen does need cleaning, you may need a special cleaner such as a Brillianize product and a lint-less soft cloth.. The standard Windex and some other household cleaners can either harm the plastic or leave residue in the fine texture. If there are fine grooves, work the cloth in the direction of the grooves, not across them.

There are likely better and more comprehensive directions than these somewhere, but I thought I’d offer a bit of what I remember.