Unable to access designer 2.5.1 "The call failed on the server"

I have had this happen a couple times now, I am unable to get the designer to load and received the attached info message

“500 The call failed on the server; see server log for details”

I did received this message a couple times but the designer still loaded, but a couple times including tonight the designer never loads. Tried using chrome, microsoft edge and internet explorer.

Have others experienced and how do we fix?