FG1500D 5.2.13 out-of-sync

The image you attached is too small to read off any characters. But HA a-p "out-of-sync" doesn't necessary mean config change on the active unit doesn't get copied over. You can check it by getting in to the slave side to see the config you changed on the active.

Earlier version of 5.2 had HA related problems so we had to migrate all clusters to 5.4 after 5.2.9, which I don't remember what was exactly the main issue..We hit at least two HA related bugs by that time and I think all of them were fixed in later 5.2.x.

Anyway, only thing you can try to see if it fixes it is manually re-calculating checksum on both master and slave units. We still have to do this time to time with 5.4 on some cluster for whatever the reason is. You might need to do it a couple of times especially on the slave unit.

If 5.4, the CLI is "diag sys ha checksum recalculate" but I know 5.2's CLI was slightly different. Try the 5.2 equivalent CLI then if checksum still doesn't match, you should open a ticket with TAC to get both config compared. There must be a reason the config can't match.