Build Number: 9292.1665972
In campaign battles with a supporting army on either side the buffs used by supporting generals such as: Commander - Unyielding Earth/Stone Bulwark/Inspiring words, Sentinel - Adamant Resolve: do not take away the stat line buffs when they end. This has happened twice when I fought Ai supporting Commander generals using Unyielding Earth which has trapped my general in an impossible duel with them both times because the melee evasion never went away and even continued to stack higher as the duel dragged on. The stats are also kept for any units affected, not just the casting general or other generals.
Reproduction has been as easy for me as to have a buff capable general in a supporting army and using any of the above buff skills. I assume other similar stat buffing skills such as Sentinel - Tempered Reflection would also cause this issue but I don't have a save to test them.
I am including a battle replay showing the NOT reinforcing Commander - Stone Bulwark buffs expiring as expected along with the Sentinel - Adamant Resolve NOT expiring twice in a row, raising the melee evasion of every unit affected over 100% permanently. I am also including the campaign save before the siege battle at Nanhai - City I used to test for myself with one army having a Commander - Liu Bei and Sentinel - Jian Yong with abilities that will trigger this bug. As long as either is in the reinforcing second army during the battle the stat buffs of their abilities will be permanent and as long as they are in the main army their stat buffs will end as expected when they time out. Lastly the Unbreakable effects do not seem to stay permanently when the bugged stats are kept so this seems specifically related to stat changes caused by reinforcing generals.