Setting channel plan with web tool

We have several RAK 7268 (with various FW versions) and when we try to config the channel plan we encounter strange behavior from the WEB configuration tool.
We switch to the advance mode and try to set the channel manually but the UI does not let us or make the change as we want.
For example , here (Version 1.1.2_RAK rRAK-b5615257b), the first channel say 904.7M while it should be 903.9M, and when I try to change the If it suddenly switch to 903.9 but does not save it from some reason.