Running balance stops working

[AC]

I was just entering mutual funds into one of my accounts and the balance
column now has a blank space for the last transaction (currently using
version 2.6.3)

I've deleted the transaction and added it again with no luck.

The only thing unusual in my case is that I added a different namespace
for the fund symbols because I'm not using the online tools.  I just
wanted to have these funds in a different namespace from "FUND".  There
are several hundred transactions in this account and all show a balance
but as soon as I add a new one it goes blank.


I also tried testing by duplicating an existing transaction which looks
ok.  The result is the same, a blank balance field.