When running with workers, you may encounter some issues specific to this mode:

• If you get strange errors when running with workers, with wkhtmltopdf not working as intended (for example, prematurely exiting with a -11 or -6 status), then you likely have limit_memory_hard set to a value that is too low. Try raising it a bit, as the default value is notoriously too low.
• If you get timeout errors when performing long operations (this includes CSV imports and exports and add-on module installations), try increasing the limit_time_cpu and limit_time_real parameters, as there, too, the default value is quite low. If you have a reverse proxy, you may want to check its timeout limit too (too low a limit in the reverse proxy will not prevent the transactions from completing, but will display an error message in the user's browser, which can cause them to retry the import and unnecessarily put a load on the server).
• If your instance gets completely stuck when printing reports, try raising the number of workers. This can be a deadlock caused by wkhtmltopdf blocking up all the available workers while printing.