Description:
i am experiencing some strange behavior with copy and paste.
On Document A I can do a CTL -A , CTL -C; followed by a CTL -A, CTL -V, on document B; to create a mirror document.
The problem lies with copying and pasting individual words; or groups of words.
I used to SIMPLY double-left-click; highlight; and then copy a word in document A; followed by double-left-clicking; and highlighting the target word in document B; followed by a paste command.
NOW if I double-left-click the word BIG in document A; and then do a CTL -C; followed by double-left-clicking the word SMALL in document B; followed by a CTL -V; the word SMALL quickly disappears, and then reappears.
An ordinary copy and paste will work if I double-left-click; highlight; and then copy a word in document A; followed by positioning the cursor before the target word, in Document B; with a SINGLE left click; being careful not to highlight it with the click; and then do a paste command; followed by a deletion of the old word.
A WORK-AROUND I found for copy, cut, and paste is to position the cursor before BIG, in Document A; with a SINGLE left click; being careful not to highlight it with the click; and while HOLDING the left button down, highlight the word BIG. I then did a CTL -C. Then I positioned the cursor before the word SMALL, in Document B; with a SINGLE left click; being careful not to highlight it with the click; and while HOLDING the left button down, highlighted the word SMALL. I then did a CTL -V. The word SMALL changed to the word BIG.
After extensive Google searches, I believe that this has something to do with what had control of the clipboard last.
Before all of this strange behavior, I could cut a section of words; do a CTL -f to find the new insertion point; and then do a paste.
NOW, if I do a cut; and a CTL -F; I lose what was in the cut; and paste only what I searched for with CTL -f.
Different results occur after highlighting an entire document with CTL -A; and highlighting a word, or group of words, with a double-click.

Actual Results:  
NOW if I double-left-click the word BIG in document A; and then do a CTL -C; followed by double-left-clicking the word SMALL in document B; followed by a CTL -V; the word SMALL quickly disappears, and then reappears.

Expected Results:
An ordinary copy and paste will work if I double-left-click; highlight; and then copy a word in document A; followed by positioning the cursor before the target word, in Document B; with a SINGLE left click; being careful not to highlight it with the click; and then do a paste command; followed by a deletion of the old word.


Reproducible: Always

User Profile Reset: No

Additional Info:


User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:54.0) Gecko/20100101 Firefox/54.0