Sometime "S7 in" node failed to read data from S7-1200 PLC

Hello everyone,

I have a difficult point with "S7 IN" node when I read data from S7-1200 PLC via IOT2040.

Normally I can read data from PLC by using "S7 IN" node, but sometime the "S7 IN" node can post an error message "Failure (Bad values)", it seems like IOT lost connection with PLCs within several seconds. If at that time the IOT is reading data from PLC, the data will be lost.

The IOT is connecting with 5 PLC and there are about 10 variables can be read from every PLC .
Every PLC can throw the error.

Attachment is the error message picture.

Anyone knows the reason? Share with me pls!

Thanks in advance!