I believe this started in 14.0.4, but it persists in 14.0.5...I've been getting a completely blank Summarizing field window most of the time when fields are summarizing on a layout. I'm connecting to a remote solution that does a lot of bad summarizing (it's something I've actually been charged with fixing – but the issue is making it difficult to identify the culprit fields), and I get this white rectangle of the exact dimensions of the summarizing window in the middle of my screen (annoyingly, and probably against OS X standards, this window persists when I switch to other applications). I can cancel the operation with a command-period or the escape key, but it's really annoying and it's hampering my work.
Here's an example:
I just replaced my iMac; it happened on the old one and it happens on the new one. I've deleted and reinstalled FMPA (though not prefs yet – hoping to avoid that). It's also happening on my MacBook Pro. Only seen it on El Capitan so far.