我也遇到了类似的问题，不过是断电后通电重启的时候，PLC处于STOP状态，需要手动把状态开关掰到stop然后再打到run状态就好。run前后两次读取的诊断缓冲区不同，run之前读取诊断缓冲区如下，注意时间成了1994年1月1号。
Diagnostic buffer of module CPU 319-3 PN/DP

Order No./ Des cription Component Version
6ES7 318-3EL01-0AB0 Hardware 5
- - - Firmware V 3.2.6
Boot Loader Firmware expansion A 35.9.9

Rack: 0
Slot: 2


Serial number: S C-C2U581062012


Event 1 of 31: Event ID 16# 38C4
Distributed I/Os: station return
Address of the affected DP slave: station number: 65
DP master system ID: 1
Log. base address of the DP slave: Input address: 8188
Log. base address of the DP master: 8190
Requested OB: Rack failure OB (OB86)
OB not found, or disabled, or cannot be started in the current operating mode
External error, Outgoing event
12:00:38.934 AM 01/01/1994
(Coding: 16# 38C4 FE56 C054 1FFE 1FFC 0141)


Event 2 of 31: Event ID 16# 38C4
Distributed I/Os: station return
Address of the affected DP slave: station number: 64
DP master system ID: 1
Log. base address of the DP slave: Input address: 8173
Log. base address of the DP master: 8190
Requested OB: Rack failure OB (OB86)
OB not found, or disabled, or cannot be started in the current operating mode
External error, Outgoing event
12:00:33.172 AM 01/01/1994
(Coding: 16# 38C4 FE56 C054 1FFE 1FED 0140)


Event 3 of 31: Event ID 16# 38C4
Distributed I/Os: station return
Address of the affected DP slave: station number: 42
DP master system ID: 1
Log. base address of the DP slave: Input address: 8171
Log. base address of the DP master: 8190
Requested OB: Rack failure OB (OB86)
OB not found, or disabled, or cannot be started in the current operating mode
External error, Outgoing event
12:00:33.091 AM 01/01/1994
(Coding: 16# 38C4 FE56 C054 1FFE 1FEB 012A)


Event 4 of 31: Event ID 16# 38C4
Distributed I/Os: station return
Address of the affected DP slave: station number: 38
DP master system ID: 1
Log. base address of the DP slave: Input address: 8181
Log. base address of the DP master: 8190
Requested OB: Rack failure OB (OB86)
OB not found, or disabled, or cannot be started in the current operating mode
External error, Outgoing event
12:00:33.011 AM 01/01/1994
(Coding: 16# 38C4 FE56 C054 1FFE 1FF5 0126)


Event 5 of 31: Event ID 16# 38C4
Distributed I/Os: station return
Address of the affected DP slave: station number: 36
DP master system ID: 1
Log. base address of the DP slave: Input address: 8182
Log. base address of the DP master: 8190
Requested OB: Rack failure OB (OB86)
OB not found, or disabled, or cannot be started in the current operating mode
External error, Outgoing event
12:00:32.928 AM 01/01/1994
(Coding: 16# 38C4 FE56 C054 1FFE 1FF6 0124)