I tested this with 128.6.1esr and 135.0b4. It seems that the problem occurs when the new mail notification is not displayed. I identified two cases, thought there may be others (such as the one mentioned in [comment 1](https://bugzilla.mozilla.org/show_bug.cgi?id=1850289#c1)): 1. The "Show an alert" option in "When new messages arrive" is unchecked. 2. Clicking on the "Get new messages" button I was able to reproduce the issue consistently. [Here]() you could find the full thread in the addon dev room. You can find the [full thread](https://matrix.to/#/!IfvTkjNTPAqwpygthx:mozilla.org/$Pn4JbY8B_XeyLdTymnPCPBTu8lUgK1_AGURBh_79Ygs?via=mozilla.org&via=matrix.org&via=poellmanndaniel.de) in the add-on dev room.
Bug 1850289 Comment 12 Edit History
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I tested this with 128.6.1esr and 135.0b4. It seems that the problem occurs when the new mail notification is not displayed. I identified two cases, thought there may be others (such as the one mentioned in [comment 1](https://bugzilla.mozilla.org/show_bug.cgi?id=1850289#c1)): 1. The "Show an alert" option in "When new messages arrive" is unchecked. 2. Clicking on the "Get new messages" button I was able to reproduce the issue consistently. You can find the [full thread](https://matrix.to/#/!IfvTkjNTPAqwpygthx:mozilla.org/$Pn4JbY8B_XeyLdTymnPCPBTu8lUgK1_AGURBh_79Ygs?via=mozilla.org&via=matrix.org&via=poellmanndaniel.de) in the add-on dev room.