Not sure if this is the same, but it sounds similar to something I have 
experienced in recent squeaks. See if this helps at all:

'From Squeak5.1 of 23 August 2016 [latest update: #16548] on 3 November 
2018 at 9:50:50 pm'!

!TextMorphForEditView methodsFor: 'event handling' stamp: 'raa 11/3/2018 
21:50'!
keyStroke: evt
     | view |
     editView deleteBalloon.
     (editView scrollByKeyboard: evt) ifTrue: [^self].


     [(evt controlKeyPressed
         and: [evt commandKeyPressed]
         and: [evt keyValue = 28 or: [evt keyValue = 29]]
     ) ifTrue: [
         ^self    "funky trackpad code scrolls - yecch"
     ].] on: Error do: [ :ex | ].



     self editor model: editView model.  "For evaluateSelection"
     view := editView.  "Copy into temp for case of a self-mutating doit"
     (acceptOnCR and: [evt keyCharacter = Character cr])
         ifTrue: [^ self editor accept].
     super keyStroke: evt.
     view scrollSelectionIntoView.

     "Make a cheap check and guess editing. (Alternative would be to 
copy the old contents and then compare them against the new ones. Maybe 
add a better hook in the TextEditor."
     (self readOnly not and: [evt keyCharacter isAlphaNumeric or: [evt 
keyCharacter isSeparator]])
         ifTrue: [view textEdited: self contents].! !


On 11/3/18 5:44 PM, Chris Muller wrote:
> Hi Eliot and all,
>
> I have just noticed in Squeak 5.2 that attempting to scroll a text
> pane beyond its scroll limit causes the text cursor to start moving.
> So, for example, when I have a selected expression in the debugger,
> and I simply scroll the text pane, I hit the end and lose the
> selection, which is incredibly annoying.
>
> Does anyone know why this is and how to fix it?
>
> Thanks
>

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