Carette compressor issues

[Aldea6]

 I have a Carette compressor for 5 years now and it worked great to fill my CF bottle up to 300 bars. But now , it cannot reach more than 220/240 bars . The compressor is running , but the pressue doesn't increase . I' sure there is no leaks in the air circuit . I checked and clean the check valve on the HP cylinder , and the one at the entry of the air/oil separator .I also checked the low pressure cylinder assembly , same with the high pressure cylinder. Replace the brass seal of the check valve .
 When I start the compressor until 200 bars , then switch off , there is some air leaking through the intake air filter , on top of the low pressure cylinder. No leaks on the pressure lines or anywhere else , so I suspect the check valve at the bottom of the air/oil separator , or the check valve on top of the high pressure cylinder.
I just try to understand what's the problem.

If somebody had an idea on what's go wrong he's welcome .

[bnowlin]

I would think it is the butterfly valve reed in the high pressure and or the compressor ringd worn out.
Bpb