Created attachment 134676 [details]
zip file with test documents and several screenshots

In LO Writer from builds younger (!) than

libo-master64~2017-07-12_23.21.39_LibreOfficeDev_6.0.0.0.alpha0_Win_x64.msi
resp.
libo-master~2017-07-13_05.02.25_LibreOfficeDev_6.0.0.0.alpha0_Win_x86.msi

I have the problem, that Writer "freezes", when I make some changes in my edited documents. Writer doesn't answer and in the Task Manager I see, that the program uses many cpu capacity.
Sometimes the programs wakes up alone after a certain time (some minutes) without any actions, but mostly it doesn't.
But I have seen, that it wakes up often (but not allways) after I have made and saved a screenshot with "Snipping Tool". Then cpu of LibreOffice decreases to 0 or near 0 and Writer answers again.

For demonstration I have edited my test document "Test_Altix V - Abbau des Kameradeckels.odt" (in the attached zip file) without any problems with
Version: 6.0.0.0.alpha0+
Build ID: d9e8fdbcd2f834a483890b409ede1b44c2da5da3
CPU threads: 1; OS: Windows 6.19; UI render: default; 
TinderBox: Win-x86@42, Branch:master, Time: 2017-07-13_05:02:25
Locale: de-DE (de_DE); Calc: group

The saved document with my changes is "Test_edited+saved_Altix V - Abbau des Kameradeckels.odt" (also in the zip file).

Than I have tried to do the same with
Version: 6.0.0.0.alpha0+ (x64)
Build ID: f054b9187155bc32b7d06808aea87127cb0a3a4f
CPU threads: 2; OS: Windows 6.19; UI render: default; 
TinderBox: Win-x86_64@42, Branch:master, Time: 2017-07-15_22:51:09
Locale: de-DE (de_DE); Calc: group
and
Version: 6.0.0.0.alpha0+
Build ID: c7fe625c8d41f648f89765abc40bb7b8fd4ed12a
CPU threads: 1; OS: Windows 6.19; UI render: default; 
TinderBox: Win-x86@42, Branch:master, Time: 2017-07-16_02:04:02
Locale: de-DE (de_DE); Calc: group

and I got the freezes, see several screenshots in "Screenshot_x64_*.*_(Loop)_Writer_Problem.JPG" (also in the zip files).
 
I have tested on both an old computer with x86 cpu and a newer with x64 cpu.
 
Steps to reproduce:
- open "Test_Altix V - Abbau des Kameradeckels.odt"
- copy the lines according to "Screenshot_1_Writer_Problem.JPG" at the end of the document (see "Screenshot_2_Writer_Problem.JPG")
- change the copied lines according to "Test_edited+saved_Altix V - Abbau des Kameradeckels.odt" resp. "Test_edited+saved_Altix V - Abbau des Kameradeckels.pdf" (= odt document exported to pdf)

- after one enters some characters Writer stops, not answers on any actions, but uses many cpu time (only with "younger" builds of LO)
- when Writer freezes longer, making a screenshot may help to wake up Writer