Using scaffolding to build, but needing to press shift-click on certain blocks causes you to descend into the scaffolding. To counteract this, you press Jump and shift at the same time (creative mode trick) but on scaffolding it causes a "bouncing" view that makes placing blocks complicated. Jump + shift on scaffolding should work like it does elsewhere to lock you in place.
Thank you for your report!
We're actually already tracking this issue in MC-143226, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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