I know many users are affected by the Lighting rendering issues due to custom formula fields (see Known Issue link, closed as "No Fix" with 77 reporting). I've had a Case with Salesforce Support over the past few weeks because contrary to that Known Issue writeup, it's doesn't just depend on the fields in your page layout. If you store formula fields in another component on your record page (such as in a Field Set, or any future created component), the Lighting Record Page will fail to load because it can't handle complex formulas.

I requested the Known Issue be updated, but in in the interim I want to save others from wasting time on this, and it's not possible to comment on Known Issues.

*Lightning Record Page* limitation with too many formula fields with complex formulas