"0xe550C" Error for iOS device with IdP(PAC)

Hello there

I have multiple customers who reported about the error “0xe550C” for iOS devices.
Ref: Troubleshooting SAML | Zscaler

The common points are followings.

  1. the end users use iOS device. (No report from windows user)
  2. Traffic Forwarding Method is PAC File. (One of customers uses PAC over GRE)

No matter their IdP, they face this issue on Safari.

A weird point is the issue is observable NOT 100% but frequently.
Some customer reports this issue is seen once a week.
Other one says this is seen 3 times in 5 times.

Every time we open a support ticket, then we receive the same answer: “Please collect header trace”.
End user is uses iPhone either iPad. Those devices do not have developer tool or inspector. They need to have Mac OS device to use such.

Anyone else has seen this issue before? If you have any knowledge to resolve this, please could you teach us how you fixed it?

Thanks in advance!
Best regards,