Slow uploads through BIG-IP

First thing is to understand at which layer is the delay. Is that because of interfaces errors, TCP settings, HTTP profile, etc...

Interfaces errors, if easy to check in the interface status.

tmsh show net interface

For TCP, you need to get a tcpdump in the F5, and look for transfer pauses, zero windows size, etc..

For HTTP profile, is easy to rule out, just remove the profile from the virtual server and any client ssl or serverssl. You could also change the virtual server to forward IP, in case you are using the default standard type.

After you narrow down the problem, is easy to give a suggestion about what could be.

For tcpdump, check this solution:

https://support.f5.com/csp/article/K411