Changing the source would just instruct the panel to listen to the unencrypted transmission of any S-line sensors, and I wouldn’t expect that to have any impact on what you are reporting.
Do the smoke detectors themselves beep and flash their status LED? There are other conditions for some smoke detectors specifically that will cause an Offline supervisory trouble, like a dirty sensor status. The frequency of local LED flashes while a sensor beeps tells you what the status is. From the IQ Smoke Detector manual:
The first general step I would recommend is to follow Tyler’s recommendation regarding firmware. The panel is on very old firmware for the IQ Panel 4, so you would need to update incrementally. 4.2.1 > 4.3.0 > 4.4.1 > 4.5.2 > 4.6.1
I would recommend updating to at minimum 4.4.1. A guide with the necessary patch tags for each version is linked below: