Can you create a new profile https://support.mozilla.org/en-US/kb/using-multiple-profiles to see if this reproduces with beta archive.mozilla.org/pub/thunderbird/releases/90.0b2/ ? beta implements new ldap code https://www-stage.thunderbird.net/en-US/thunderbird/90.0beta/releasenotes/
Bug 1626944 Comment 10 Edit History
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Can you create a new profile https://support.mozilla.org/en-US/kb/using-multiple-profiles to see if this reproduces with beta https://archive.mozilla.org/pub/thunderbird/releases/90.0b2/ ? beta implements new ldap code https://www-stage.thunderbird.net/en-US/thunderbird/90.0beta/releasenotes/