Pls do not disable CloudFlare. Disableing something is never a solution but more a “workaround”.
Here I opened the same topic half a year ago and solved it.
https://community2.invoiceplane.com/t/topic/7870
Pls have a read and try to solve it like this. But disabeling something always brings disadvanteges.
CloudFlare for example hides the IP of your origin Server and boosts the speed and security of your Server and Application.