Setting keyboard input source change shortcut to Shift + Shift R causes problems in some text entry widgets

[circum]

Set the next text entry source shortcut key (System Settings -> Text Entry) to "Shift + Shift R", i.e., pressing both shifts together.

With this setting, some input entries have problems with pressing the Shift key inside: I experienced errors with gedit's find input entry, nemo's file rename in-place edit entry and firefox's in-place edit entry when renaming a Google Sheet's tab.

I refer to the detailed description and how it is reproducible in the following bug report:

https://bugs.launchpad.net/ubuntu/+source/nemo/+bug/1409353

Copy-paste from there:

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Since upgrading my Ubuntu box to 14.04 from 13.10, I have encountered with this weird behavior.

I can reproduce the error with the following scenario:

start nemo
press shift-ctrl-n to create a folder. A new folder with 'Untitled Folder' created, the name is selected as an editbox to rename it.
press shift-ctrl again. The order is important -- shift before, ctrl after. The selection goes away, and now the folder 'Untitled Folder' itself is selected.
after that, you cannot cut or copy -- neither with keyboard shortcut, neither with menu items. As nemo visually gives feedback upon cutting a file, I can see that the cut action is not performed.

Alternatively, you can simply try to enter an uppercase letter in the rename edit box -- i.e., press shift-A. The character is not inserted, the rename action is finished, and copy-paste does not work.

nemo version: 2.4.4-2~webupd8~trusty0
[...]
I have found the triggering condition on my box: I have set the next text entry source shortcut key (System Settings -> Text Entry) to "Shift + Shift R", i.e., pressing both shifts together. If I remove this shortcut, then the problem disappears.
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I have also found the following description related to this issue (in fact, it was the post helped to identify the root cause for me):

http://askubuntu.com/questions/523937/shift-any-key-combination-closes-search-dialog-in-gedit-on-14-04

Possibly this (already closed) one was also connected with this issue, and was fixed by some other workaround:
https://bugs.launchpad.net/ubuntu/+source/nautilus/+bug/1322925

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Ivan Toshkov (itoshkov)]

The bug is still present in 15.04.