The checksum does not match when receiving rtcm messages between two ublox ZED-F9P

[isrigorev]

Describe the bug

I'm using two ublox F9P, one configured as a base and the other as a rover. Ntrip server configured using pygpsclient. Checksum error appears when connecting using ntrip_client

[WARN] [1727698883.841775]: Found packet, but checksums didn't match
[WARN] [1727698883.842424]: Expected Checksum: 0xFF00
[WARN] [1727698883.843070]: Actual Checksum: 0x81688F
[WARN] [1727698883.843736]: Found packet, but checksums didn't match
[WARN] [1727698883.844369]: Expected Checksum: 0x1
[WARN] [1727698883.845008]: Actual Checksum: 0x91185E
[WARN] [1727698883.845643]: Found packet, but checksums didn't match
[WARN] [1727698883.846262]: Expected Checksum: 0x0
[WARN] [1727698883.846871]: Actual Checksum: 0xF1A64F

At the same time, when using a client connection via pygpsclient, there are no errors, packets arrive. Everything works similarly when connected via u-center

To Reproduce
Steps to reproduce the behavior:

1. Launch Node with command roslaunch ntrip_client ntrip_client.lauch
2. Successfull connection to server
3. See Error

Expected behavior
checksums must match

Environment (please complete the following information):

• OS: Ubuntu 18.04
• Architecture: x86_64
• ROS Version: noetic
• Version: 1.0.0
• Sensor(s): ublox ZED-F9P

Modifications
No modifications

[isrigorev]

it seems that packets that pass the sum check are also present, they just alternate with those that fail