I suspect you are confusing two things.
A fully charged 24v battery when left standing with no load and no charge should read about 25.2v so if you are measuring things under those conditions all is well.
As soon as you start to charge the volts should rise and with plenty of charge and no controller to limit it it should get to over 28V.
With a small intermittent charge as you have for considerable periods it will be somewhere below 28v depending on the current. With a decent current going in (say 10A) for a few minutes you should be going over the 28v and start gassing.
If that is what you see then all is well.
Leave the battery with no load and no charge for 12 hours and if it is over 25.2v you don't have a problem.
Batteries are confusing things and I still don't understand all their strange goings on after 50 years. You will learn what volts to expect depending on whether they are charging or discharging and those voltages will be unique to your batteries.
All these voltage tables available everywhere are at best a guide and some batteries never seem to have read the table.
Flux