Yuri, Modot lets create a VRS by picking a lat and lon and time frame. They can deliver it in many Rinex formats. Attached is a Rinex2.11 file for VRS in my area. I thought it might give you some insight into what they are doing.
To get a decision I need a data. Could you collect some data for this issue - start JMobile RTK rover and activate recording raw data logging and into a jps file, and set Store Base Correction check mark in file logging settings.
Then go to RTK Survey and in settings set check mark "Debug mode".
Then survey a point with known coordinate.
Send me the job with raw data and debug info inside.