Answer
Check which Report Rules are currently active for that specific report and try temporarily deactivating them one at a time to see whether one of them is what's actually causing the delay — Report Rule evaluation itself can be a hidden source of slowness that isn't visible as an 'error,' just added time. Also keep in mind that a Reprint Modified action re-executes the report's own underlying logic (not just the print/PDF step), so if deactivating Report Rules doesn't isolate it, add tracing to the report's own logic (the report view/procedure behind it) to check whether the slowdown is actually inside the report's data-gathering logic rather than anything print-related.