From #494 (comment)

For the other account (which contains mails with all kinds of DKIM
status, but most mails should have a valid DKIM signature),
the status of all mails is "Internal error",
and the TB error log contains

DKIM_Verifier.Verifier FATAL Error during DKIM verification: Error: An unexpected error occurred verifier.mjs.js:1499:8
#handleException moz-extension://458239d6-c7cc-4e68-83c6-1dbff2fea153/modules/dkim/verifier.mjs.js:1499
#processSignatures moz-extension://458239d6-c7cc-4e68-83c6-1dbff2fea153/modules/dkim/verifier.mjs.js:1541

for every DKIM verification attempt.

Complete error log with a freshly restarted TB and debug enabled:

UnknownCollectionError: Unknown Collection "thunderbird/url-parser-default-unknown-schemes-interventions"
UnknownCollectionError resource://services-settings/RemoteSettingsClient.sys.mjs:189
sync resource://services-settings/RemoteSettingsClient.sys.mjs:635
SimpleURIUnknownSchemesRemoteObserver.sys.mjs:114:15
#getBypassListSettings resource://gre/modules/SimpleURIUnknownSchemesRemoteObserver.sys.mjs:114
services.settings: Remote Settings startup changesets bundle could not be extracted (TypeError: serverInfo.capabilities.attachments is undefined) remote-settings.sys.mjs:225
services.settings: UnknownCollectionError: Unknown Collection "thunderbird/remote-permissions"
UnknownCollectionError resource://services-settings/RemoteSettingsClient.sys.mjs:189
sync resource://services-settings/RemoteSettingsClient.sys.mjs:635
RemoteSettingsClient.sys.mjs:555
services.settings: UnknownCollectionError: Unknown Collection "thunderbird/third-party-cookie-blocking-exempt-urls"
UnknownCollectionError resource://services-settings/RemoteSettingsClient.sys.mjs:189
sync resource://services-settings/RemoteSettingsClient.sys.mjs:635
RemoteSettingsClient.sys.mjs:555
DKIM_Verifier.Verifier DEBUG 1 DKIM-Signatures found. verifier.mjs.js:1519:8
DKIM_Verifier.Verifier DEBUG Verifying DKIM-Signature 1 ... verifier.mjs.js:1534:9
DKIM_Verifier.Verifier DEBUG Parsed DKIM-Signature 1:
Object { original_header: "DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=vbl.de; s=default;\r\n\tt=1741593510; h=from:from:reply-to:reply-to:subject:subject:date:date:\r\n\t message-id:message-id:to:to:cc:mime-version:mime-version:\r\n\t content-type:content-type; bh=tN+HR7z2EDBLTCMTGKF62peQRnRTUk2GH4ZF9FAmsik=;\r\n\tb=CHJieycuj3UMLTvWQgbo+bpiv+ePKaM3/vY8DpyZhqH6Q8r+rb2VOas4wEJsSeeaCdmyN1\r\n\tI0NZOmYgGJo/Ze096+QNJp9Kk+OHk2QKzRnfScYD2wdqeEJ9ehWCiuC1dpf9VnqHsTl1pL\r\n\tYGnT/UFSv/H0xqaF3qoG0llRlkm9/F5hJBkuTcH0D5vFSipE9MxcNHizq//3z+KwwY5GcZ\r\n\tS5cAoLvHLPfC9jhjdgvy6v83RCUiyANEhbH4xQUodfmkSLIqzD6mN5zMPXkcs5U8UvhOFB\r\n\tl71dLAuAOn7GUG8t8SeuQAGBZxP60Ofa8ytUkfsOQZd3Bsd8dDuUVFvoiCQMew==\r\n", v: "1", a_sig: "rsa", a_hash: "sha256", b: "CHJieycuj3UMLTvWQgbo+bpiv+ePKaM3/vY8DpyZhqH6Q8r+rb2VOas4wEJsSeeaCdmyN1I0NZOmYgGJo/Ze096+QNJp9Kk+OHk2QKzRnfScYD2wdqeEJ9ehWCiuC1dpf9VnqHsTl1pLYGnT/UFSv/H0xqaF3qoG0llRlkm9/F5hJBkuTcH0D5vFSipE9MxcNHizq//3z+KwwY5GcZS5cAoLvHLPfC9jhjdgvy6v83RCUiyANEhbH4xQUodfmkSLIqzD6mN5zMPXkcs5U8UvhOFBl71dLAuAOn7GUG8t8SeuQAGBZxP60Ofa8ytUkfsOQZd3Bsd8dDuUVFvoiCQMew==", b_folded: "CHJieycuj3UMLTvWQgbo+bpiv+ePKaM3/vY8DpyZhqH6Q8r+rb2VOas4wEJsSeeaCdmyN1\r\n\tI0NZOmYgGJo/Ze096+QNJp9Kk+OHk2QKzRnfScYD2wdqeEJ9ehWCiuC1dpf9VnqHsTl1pL\r\n\tYGnT/UFSv/H0xqaF3qoG0llRlkm9/F5hJBkuTcH0D5vFSipE9MxcNHizq//3z+KwwY5GcZ\r\n\tS5cAoLvHLPfC9jhjdgvy6v83RCUiyANEhbH4xQUodfmkSLIqzD6mN5zMPXkcs5U8UvhOFB\r\n\tl71dLAuAOn7GUG8t8SeuQAGBZxP60Ofa8ytUkfsOQZd3Bsd8dDuUVFvoiCQMew==", bh: "tN+HR7z2EDBLTCMTGKF62peQRnRTUk2GH4ZF9FAmsik=", c_header: "relaxed", c_body: "relaxed", d: "vbl.de", … }
verifier.mjs.js:1536:9
DKIM_Verifier.Verifier DEBUG computed body hash: tN+HR7z2EDBLTCMTGKF62peQRnRTUk2GH4ZF9FAmsik= verifier.mjs.js:1285:7
DKIM_Verifier.dns DEBUG configure jsdns dns.mjs.js:92:7
Failed to load chrome://dkim_verifier_jsdns/content/JSDNS.mjs?1741596609971 jsdns.js:57:33
getAPI @.***!/experiments/jsdns.js:57
asyncLoadAPI resource://gre/modules/ExtensionCommon.sys.mjs:1368
AsyncFunctionNext self-hosted:800
DKIM_Verifier.Verifier FATAL Error during DKIM verification: Error: An unexpected error occurred
configureJsdns moz-extension://458239d6-c7cc-4e68-83c6-1dbff2fea153/modules/dns.mjs.js:94
verifier.mjs.js:1499:8
#handleException moz-extension://458239d6-c7cc-4e68-83c6-1dbff2fea153/modules/dkim/verifier.mjs.js:1499
#processSignatures moz-extension://458239d6-c7cc-4e68-83c6-1dbff2fea153/modules/dkim/verifier.mjs.js:1541
DKIM_Verifier.Verifier DEBUG Exception on DKIM-Signature 1 verifier.mjs.js:1542:9
DKIM_Verifier.SignRules DEBUG shouldBeSigned:
Object { shouldBeSigned: true, sdid: (1) […], foundRule: true, hideFail: false }
signRules.mjs.js:458:7
DKIM_Verifier.AuthVerifier DEBUG authResult:
Object { version: "2.1", dkim: (1) […] }
authVerifier.mjs.js:223:7
DKIM_Verifier.SignRules DEBUG shouldBeSigned:
Object { shouldBeSigned: false, sdid: [], foundRule: false, hideFail: false }
signRules.mjs.js:458:7
DKIM_Verifier.AuthVerifier DEBUG authResult:
Object { version: "2.1", dkim: (1) […] }
authVerifier.mjs.js:223:7
window.controllers/Controllers is deprecated. Do not use it for UA detection. 2 blank

​
This is a locally built TB 136.0 on Gentoo linux.