You are running your SRX cluster as Active-Active? This is why nothing probably makes sense. If you run SRX A/A because the SRX is stateful FW you transmit and receive path MUST be the same or else SRX drops the packet. A/A is a nice idea, but hardly anyone uses this in the real world due to exactly what you are seeing. Trying to troubleshoot A/A is extremely difficult. Can you set you SRX cluster as A/P (standby) and also take out EX AE config and then see what happens?
Did you decide on this design yourself or did you work with whomever sold the Juniper equipment?