SolarWinds Transaction Log Size Getting Bigger.

Dear ALL SolarWinds Community Experts,

We are deploying SolarWindsOrion Database in Always On High Availability Group and the SolarWinds Orion DB backup option is set to full.  We realized that the SolarWinds Transaction Log size is getting bigger and bigger.

We have tried a few solutions suggested by the SolarWinds Success Center to shrink the file. However, it was failed. 

Please advise if you have a solution. Much appreciated your help.