GaryMfield said

I have many tasks that I set with a reminder. Some of the tasks I continue to push out to new dates as they are low priority. Every so often, the oldest tasks quit showing the reminder. Currently, I have 23 tasks that should be showing in the task reminder window but only 16 are showing. The 7 that are missing are the oldest. 5 from August 30 and 2 from Sept. 10. They continue to show green in the list of tasks. I am running Windows 7 Pro and am up to date on all fixes. Thunderbird is at Version 60.9.0 (32-bit). Anyone have any ideas on what might be causing this? Thanks.

Update 12/20/2019: This appears to be happening when Thunderbird or Lightning crashes with task reminders open in the reminder window. Any ideas or should I report as a potential bug? Thanks.

Is this what is happening? https://bugzilla.mozilla.org/show_bug.cgi?id=1140035

That is reminders plus or minus 90 days are not displayed which woulds similar o what you said.

Do you have any crash ids for your crashes. https://support.mozilla.org/en-US/kb/mozilla-crash-reporter-tb#w_viewing-crash-reports

Perhaps there is something there that might be relevant, at least we can look.

Thank you for the response but that is not what is happening. I don't find any current crash reports. The newest one is from February of 2019. Maybe one other bit of information will help. All of the data (email, calendar, tasks, etc.) reside on a networked drive on an IBM i server, not on the local pc. The problem only seems to occur when Thunderbird shuts down abnormally. All of the tasks that are showing reminders in the reminder window at the time of the crash, "lose" the popup reminder. ie, when I restart thunderbird, those tasks won't pop up in the window again until I reset the due date to the future. However, they do continue to show green on the tasks list. If there is something I can try or other information I can provide to help solve this, I would be happy to do so. Thanks again.