Greetings, I do not have direct experience of this issue, however from looking at past forum posts relating to signatures I see there are two aspects that may be relevant for the Kobo team to help troubleshoot:
a) what tool is used for data collection (Enketo web forms or Kobo Collect app)
b) whether the data is collected in offline mode or online mode
I can see an issue was previously fixed regarding signature/offline Enketo that may relate: Could not retrieve signature - #6 by steen_andersen
For those having this issue, how is your data being collected/submitted?
