Sharepoint site loads, everything below search bar flashes then turns white

Hi all,
Curious if anyone else has encountered this. When we create new users in 365 admin, log them into their profile for the first time and open their Sharepoint app, the bar at the top with their profile and the search bar loads, but everything underneath flashes briefly, then is replaced by a blank box.

When you press refresh, the same thing happens. The only way we've found to get past this is to send the User to a site through a web link (sites load fine, this error is homepage specific), then open their Homepage in a new tab, and keep refreshing that tab while clicking the area where the 'Next' button would be in the welcome message. Eventually, their site loads and we can talk the user through their homepage.

This error also never repeats from this point, so it potentially is the fault of the welcome message glitching new users loading their homepage. Just hoping someone else has encountered this!
Thanks in advance for the help!