IMAP sync error: JSON type must be string, but is null

Problem

First one and now another mail server gives sync errors. No issues using Thunderbird or Outlook

Context

Email Provider

IMAP Server: imap.transip.email
SMTP Server: smtp.transip.email

Setup

Mailspring Version: 1.9.1-30ef802f
Platform: win32
Account State: sync_error
Account Provider: imap
IMAP Server: imap.transip.email
SMTP Server: smtp.transip.email

  • Installation Method:
  • Mailspring Version:
    5052 [2021-05-18 15:35:02.670] [foreground] [info] [local-7293f675-1375] Running EventRSVPTask performRemote:
    5052 [2021-05-18 15:35:02.670] [foreground] [critical]

*** Mailspring Sync
*** A JSON exception occurred during program execution:
*** [json.exception.type_error.302] type must be string, but is null


12244 [2021-05-18 15:35:17.700] [foreground] [critical]


*** Mailspring Sync
*** A JSON exception occurred during program execution:
*** [json.exception.type_error.302] type must be string, but is null