It seems there is a limit to the number of fields you can put on a page layout in LEX. Am I right?  I cannot find any documentation.

We have a custom object that has an "admin" page layout with 273 fields and a "regular" page layout with 80 fields. Yes, that's a lot of fields, but there is a reason the "admin" needs to see these otherwise hidden fields. It has been working just fine in classic for the past couple years (and still does), but now the we move to lightning, the details will not load and it throws an error:

Looks like there's a problem.

We couldn't find the record you're trying to access. It may have been deleted by another user, or there may have been a system error. Ask your administrator for help.

If I remove a bunch of fields, then it works again. thoughts? Thank you