[GNC] gnucash not displaying all transactions

[Alex]

Just noticed after upgrading to 2.6.20 the following

In account view the transactions are no longer ordered in "Date Posted" 
ascending order. In fact there appears to be no sorted order. I'm 
expecting transactions going back to April 2015 and I do see at least 
one transaction going back that far on the first screen. I've observed 
this in two account views - there may be more.

As the transactions were in random date order. I elected to sort the 
account view back into ascending date order.

After which all transactions before 02/06/2017 "appear" to have gone 
missing. Including the transaction in 2015 that I observed earlier.

I then did Reports -> Account Report. All the missing transactions were 
present.

The earliest transaction I could see in account view was 02/06/2017. 
Nothing earlier. Scroll bar at top, I could scroll down about 6 times.

I clicked on this earliest transaction I could see  and amazingly the 
scroll bar moved down and the earliest transaction was now 17/02/2017. I 
repeated this "Work around" several times until I got back to my 
earliest date that I was expecting which was an Opening Balance on 
31/03/2015.

Then I noticed that the latest transaction was now 11/03/2016, I knew I 
had transactions and already seen in this session transactions dated 
upto 06/04/2018. Where have they gone?

I clicked on the latest transaction and amazingly the scroll bar moved 
up and the latest transaction was now 24/06/2016.

What appears to be happening is that

I can scroll about 6 screens. But within those 6 screens gnucash has 
filtered transactions to within a certain date range. The overlapping 
date ranges I'm seeing are

31/03/2015  through  11/03/2016
21/08/2015  through  24/06/2016
27/11/2015  through  07/10/2016
11/03/2016  through  20/01/2017
24/06/2016  through  05/05/2017
07/10/2016  through  18/08/2017
20/01/2017  through  11/12/2017
05/05/2017  through  16/03/2018
02/06/2017  through  06/04/2018

This appears to be happening on accounts where there are lots of 
transactions. I've been using gnucash since 2011 and this is the first 
time I've observed this behaviour.

Have I missed the announcement about this new feature?

Has it always been a feature and I've failed to notice it before?

Is it a feature that I've stumbled across and switched it on without 
noticing?

Any guidance will be greatly received.

Alex