Well after an hour more on charge the battery managed to get to 100%. The next time I charged it, same problem. From now on I think as soon as it reaches 99% I’m going to unplug and get on the bike.
99% is fine, you are not going to notice any difference in range, but it's prob. a good idea to leave to reach 100% every 5-6 charge cycles to prevent the battery going out of balance. Depending how old your battery is, it could be a sign the cells are beginning to lose capacity. You see the same thing happen to laptop batteries.
At 99% battery is balanced, likely only time imbalance will occur is if you only charge to 80/90% then the BMS will not even think about it or a BMS bleed resistor fails.