2022年9月，有飞机反应旅客广播音量小，有时候播放登机音乐音量存在问题，有时播放预录广播时整舱声音小，乘务员三个站位PA声音均小，乘务员站位扬声器声音也小。完成整仓的量线无果，后逐个检查客舱全部PSU，分别依次晃动PSU插头及线束，晃动55HJK座椅PSU线束时，广播音乐声音变小，检查此时PA放大器LOAD值变为02，拆下55HJKPSU进一步检查PSU线束烧蚀，为验证故障，装上55HJKPSU短接烧蚀线束，故障再现，更换55HJK的PSU，并测试正常，恢复客舱PSU及头等舱右侧行李架。至此故障得以排除。
分析是由于对地短路，分流导致音量小。
2023年7月，B-21*9飞机出现同样的问题，线路检查也发现了较多的问题。
滚动更新
SR 3-5419926574 and 4-4293247867
有飞行在使用中关于MEL 26-12-01时，需引用MEL 21-01-01-01条款，两者在APU是否可以使用上有差异，MEL 26-12-01是完全禁止APU使用，而MEL 21-01-01-01在低流量状态下有条件使用APU。为此与波音做了沟通，相关解释如下：
1. When dispatching under MMEL Item 26-12-01, due to the lack of overheat detection in a particular section of ducting between the APU and the APU Bleed Valve, APU operations are only permitted for engine starts. Because of the short time duration, the MMEL does permit the APU to be used for engine start. MMEL Item 26-12-01 therefore refers only to steps 1-5 of the (O) procedure in MMEL item 21-01-01-01.
In case of conflicts between related MMEL items, the restrictions in the MMEL Item 26-12-01 item that dispatch is intended under takes precedence. In this case it is the MMEL Item 26-12-01 Item restriction to “Except for engine start, do not use the APU for pneumatic air supply and/or electrical power.
2. 1) MEL 21-01, step 5. B applies to both prior to takeoff and prior to landing. With the left pack inoperative, the APU may be used to increase air flow. If increased airflow is desired prior to landing, the steps in 5. B below may be followed prior to the initial approach phase.
2. 2) 2) MEL 21-01, step 5. C applies to both after takeoff and after landing. If the air conditioning panel was configured by following the steps in 5. B, then the steps in 5. C should be used to reconfigure the air conditioning panel after takeoff or after landing. After takeoff, the steps in 5. C would normally be completed after flap retraction is complete and before the after takeoff check.