When I delete a thread with, e.g. N msgs:  select first message, shift-click on last msg in thread, the next msg below the thread gets selected.   Now go down e.g. 2xN msg and select them again with  shift-click.  Now only the first message is select, the next N-1 msg are not selected, the last N msg are selected again.

IMHO that a bug, I would expect that all 2xN msg are selected.

Workaround is after delete of the thread, click once on the first msg after the thread that is already automaticly selected, then the following shift-click selects all msg in the range as expected by a shift-click



Reproducible: Always

Steps to Reproduce:
1. Open a folder and expand a thread (that has N msgs)
2. Click on the 1st msg of the thread
3. Shift-Click at the last thread msg and delete the thread (next msg after thread is automaticly selected
4. Scroll down lets say 2xN msg and shift-click on this msg again.

Actual Results:  
* 1st msg, that is automaticly selected  the delete is still selected
* the next N-1 msg are not selected
* the last N msg are selected

Expected Results:  
All 2xN msg are selected from 1st automaticly selected msg to the last msg that I shift-clicked.

Message list setup:

Msg sort order: By date/time of most recent in subtree
Msg sort direction: Most recent on top
Group sort direction: decending

Aggregation: Current Activity, Threaded

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