2008 Ford F150 5.4L 3V- valve job just done- two compression checks with different results?

I'll try to keep this short but thorough enough to explain the situation.

It's an 08 F150 XLT 5.4L 3V with 140,000 miles. Timing chain tensioner on passenger side failed. Cam phasers, VCT solenoids, chain, etc. etc. all replaced with OEM Ford parts. Mechanic hand turns engine to check timing but notices a valve not moving. BOTH heads taken to a shop to be looked at, 2 valves on passenger side and 6 guides replaced. Rebuilt, crank, runs terrible. Pressure check with starter 6 of 8 cylinders since 3rd and 4th can't reach with PCM. All 6 read good. Break engine bay down a bit- pressure check valves with air compressor gauge in sparkplug hole since no PCM- holds no pressure on 3rd or 4th valve. take back apart, remaining 2 valves on passenger head broken at the tip and bent. No explanation for the cause from the shop.

So now we are here, with the passenger side head REdone, but not installed. Worried, my mechanic pressure checked with the air compressor tool the DRIVERSIDE head at 80 PSI since he can then listen for leaks with a scope. Cam and components are off so all valves should be closed. He is hearing a leak from cylinder 5 and 8 intake valves and reading medium compression on the gauge despite it passing the pressure test under crank just fine. What gives? Obviously since we have most of the engine apart at this point and this is the second go around- we are being very cautious and this is worrying him. Is leaking under these conditions normal? I plan to ask the head shop their explanation but would like to hear from other mechanics as the head shop might just say whatever they can to get out of dodge. I'm currently $3,000.00 in the hole with my truck, and it's been in the shop for 2 months. Any help is greatly appreciated!!!