Google Sheets "Loading" and "Reconnecting"

I have created a series of job sheets that have are edited templates, these are linked to a main sheet that collates all that information, from there that info is passed to 2 other sheets for further analysis and breakdown.

However the main sheet has had periods of time where the data does not flow. New information doesn't come in and no info goes out to the 2 report sheets.

At first this only happened once a week for around an hour but it is now almost always happening constantly.

This is getting extremely frustrating and happens no matter what device ANYONE is looking at these sheets on (so it it not a "clear your cache = solved" problem) .

There are roughly 500 sheets attached to the main sheet using import range to import 29 cells.

Edit: This issue is in no way similar to the Trending Issue. Clearly whoever marked it as such did not read my issue.