For some reason on this site https://mf.rps.ltd/ when viewed on a mobile the menu links are retuning errors to pages that do not exist or 404 errors.
For example under mobile, click on the Markforged Printers option and it will try and load a page called https://mf.rps.ltd/markforged-x7/undefined
However in menus, this is set up as a deadlink.
Is this a permalink issue?
Sorry to hear of the problem you are having.
For me on mobile clicking on the Markforged Printers option opens drop down submenu as shown in the attached screenshot.
Could you please test it using different browser?