This has been an issue for a long time. I’ve been trying to avoid Chromium based browsers, but Firefox seems to be unable to print a lot of web pages without cutting off the content between pages. This is Firefox specific, as it doesn’t happen with Chromium browsers. It’s really a pain in the ass when I need to print something I have to open another browser and print it from there. I see tons of complaints about this online going back for years. I just spent the past two hours trying (unsuccessfully) to print a recipe correctly. I eventually gave up, opened Edge and printed from there. The current state of web browsers is dogshit. It’s either give up all of your privacy or use broken stuff. Neither is good.
I'm genuinely sorry but I can't reproduce the effects you're describing. I generate pdfs from Firefox all the time and have never encountered an issue like this.
That's why describing how to reproduce is important.
Could there be an addon you have which is causing this problem? That would explain why it happens for you on different machines.