Is this number an ID of the microflow that you can use to find failing microflow using MendixSDK?
𝕿𝖎𝖒 𝖛𝖆𝖓 𝕾𝖙𝖊𝖊𝖓𝖇𝖊𝖗𝖌𝖊𝖓
To me, this seems like a client error: the client is polling the server for the result of an action. The server tells the client the action has failed, and the client throws this error. You should look earlier in the log to see which action failed for which reason.
Rom van Arendonk
Not sure if you found the cause of this error, but we've been getting it on our side inconsistently. The Error stack trace that accompanies the error points to a
Caused by: com.mendix.languages.expressions.ExpressionException: java.lang.NullPointerException
Caused by: java.lang.NullPointerException: null
Where an attribute that is required is null, which mendix does not accept. Mendix accepts "empty", but not null.
In our case this occurs when clicking a button that saves some data. The error would occur only sometimes.
I'm not sure why this is happening, did you perhaps have success on your side?