If unable to pull vacuum down below 5 Pa or suspect an AMH leak for other reasons, should carefully check the mass lifting speed adjustment valve assembly circled in yellow below with Snoop or other leak detection method.
It could be that the nut on the flow control valve (circled in red below) is too loose causing the internal packing of the valve or similar to leak out.
If wanting to replace these the flow control valve and check valve parts are ...
Part: 3141950
Item Desc :103496,VLV,FLOW CONTROL,10-32 PT
Part: 3141945
Item Desc : 103495,VLV,CHK,10-32,MTR IN,7PSI
*** Not setup for sale, so would need to have this setup
Can get get pricing or an official quote sent if send a request for the above part numbers directly to fluke-info@fluke.com or if not in the United States then send to flukeintlpurchaseorders@fluke.com .
You might also be able to find these parts locally. The OEM info respective to above to try and locate these ...
See this related article for other troubleshooting if suspect a vacuum leak: