Intermittent “It looks like there was a problem” Message When Generating Reports

The screenshot of the message didn't come through in your post, but "It looks like there was a problem" is Lightning's generic, unhandled-error message, so the text itself doesn't tell you the root cause. Because it is intermittent, the fastest route is to capture the underlying error the next time it happens and narrow down which layer is failing. 

1. Capture the real error. When the message appears, expand the "Show details"/"More details" link if present and copy the text and error ID. Also open the browser developer console (F12 > Console/Network) before reproducing; the failing request usually shows the real exception (for example a timeout, a limit, or an Apex/Flow error). 

2. Check whether it is a platform issue. Look at

for your instance at the time of the failures and search the Known Issues site for your feature (Reports, Service Reports, Document Builder). Intermittent errors that affect several users at the same time often line up with a performance incident or a known issue. 

3. If it's a standard Salesforce report: very large or complex reports (many rows, cross filters, many groupings, formulas, long date ranges) can hit the report run-time limit or fail intermittently under load. Try adding filters to reduce the data, running it in another browser/incognito with extensions disabled, and running it as another user with the same profile. 

4. If "generating reports" means Field Service service reports or generated documents (your tags mention Generate Document): check the template for large images, many related list sections or rich-text fields, and whether the failure is tied to specific work orders/service appointments with lots of related records, line items or attachments. Also check any Flow or Apex that runs when the report/document is created (Setup > Paused and Failed Flow Interviews, Apex exception emails, debug logs for an affected user). Testing the same record with a simpler template quickly shows whether the template is the cause. 

5. If you can reproduce it with the error ID, open a case with Salesforce Support and include the error ID, timestamp, user, instance and record Id. Support can look up the error ID in their logs. 

References: 

Salesforce Known Issues:

Salesforce Trust status:

Report limits, limitations and allocations:

Field Service service reports:

Assumption: without the screenshot, error details or confirmation of whether these are standard reports or Field Service service reports/documents, this is general troubleshooting guidance rather than a confirmed root cause. If you can share the full error text and which feature you use, the community can narrow it down.