sampling problem Philips Intellivue monitor MX800 #379

Hello, 
Thank you for your software.
We are trying to collect signals from a Philips Intellivue monitor MX800. To do this, we have connected the MIB port of the monitor to a PC via: a RJ45 cable + a RJ45 to DB9-male adapter (connecting the RJ-45 terminal 4,5,7 and DB-9 male terminal 5,2,3)+ a DB9-female to female adapter+ a DB9 male to USB cable).

After having performed the software manipulations on the monitor, the com port appears well in vitalrecorder. We collect the signals well. However the signals are under sampled (much less points than on the monitor) and sometimes points are not collected. This makes the signals very distorted compared to what the monitor displays.
Do you have an idea of the origin of this problem? Could it be a problem with the cables? The computer is recent and powerful (windows 10, 8 GB RAM, intel core i5).

Thanks in advance

Mickael Pruvost