I think this bug is also fixed by the bugfix in 1.8.10-15 of gnucash. Please install that and if the bug still occurs for you, reopen this bug report and I will see what I can figure out.
The bug still occurs with -15 and the G26 theme. I can work fine with another theme, like Geramik. Looks like a problem in the G26 theme to me.
Martijn Pieters
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