I don't believe it will be fixed until build 876. 875 for browsers was already released before it was acknowledged as a TWS issue so unless a later revision of 875 gets a fix its not happening until TWS 876.
Returned back again to TWS872.6, and everything is fine now. For the time being, I can use 872 instead, but this remains a problem. If some time in the future, IB requires all clients upgrade to a higher version and this problem has not been solved, then there will be some real mess. So anyone know how to make sure it is a TWS bug or 3rd party software problem. I am not a computer expert but it seems to me that since 3rd party softwares remain unchanged and the problem occurs after TWS was upgraded to a new version, the reason of the problem is more likely to be lying on TWS' end. Maybe IB programmers need to compare the version 872 (which has no problem in this backfill issue ) with higher versions, and find out what is the problem related to this specific problem within the latest upgrades.