Field Maps JSON Parser invalid Token

[DamianSmith]

I'm running into an issue with one of my web maps, created in ArcPro 3.0.x.  The map had been working until recently. I made some changes to some labels, saved it and it continued to work. However, I recently went into Field Maps and received the following error message "JSON PARSER TOKEN INVALID". I went in and removed the label changes and saved the map in ArcPro. However now in addition to this error message on attempting to Open my map. I can only save my map as Exploratory in Arcpro. This map has before now always been an editable map.  

We're only getting this error on this map. Does anyone have any suggestions as to the root cause of the issue?  The other maps I've created are all accessing some of the same web features layers and those maps continue to function properly. Any suggestions would be appreciated. 

[DamianSmith]

I forgot to mention that when I went into Field Maps Designer, the forms for my web feature layers were gone. I recreated them, edited, and saved them.  When I went to work on another map and finished with that. Went back to the map, I'm having issues with opening and the forms were gone again

[LeviCecil]

I'm having this exact same issue. Forms are gone, and when I resave them, they don't actually save and I can't open the map in Field Maps. I'm just seeing "JSON PARSER TOKEN INVALID"

[JeffPace1]

did you ever find a solution? we have this error at enterprise 11.2, did not occur at 10.9.1