Looks like the right Si sonar is weak. Is there anything blocking the right Si sonar on your boat like the motor, a kicker/trolling motor, ladder, another transducer, the boat’s hull,…?
Can you test your unit on another boat that has a Humminbird Si unit? It does not have to be another 898c Si unit and can be a 797, 798, 997, 998, 1197, or 1198. Just be sure to plug in only the transducer and power cable for the test.