Internal server error (PDF to PPTX export)

I am working with PDF file of 43 pages (18.2 mb). For some reason we get 500 error during its export.

Error could be solved if I reduce the number of pages required for the export.

{
requestTrackingId: 'tJEXfIuVZnonTHw1J0sqmtujeg2DB7zt',
statusCode: 500,
name: 'ServiceApiError',
errorCode: 'INTERNAL_SERVER_ERROR'
}

In the unit description I see that "Per API request for a single document output, up to 50 pages". Are there any additional limitations and requirements to check before the export?