Hi Anatoly.
In case you haven't seen my other reply: my name is Hongli Lai, and I am the CTO of Phusion and main developer behind Phusion Passenger. We noticed this topic moments ago. As I've mentioned in my other reply, we take pride in writing stable, robust, well-performing software, whether we charge for it or not. The open source version of Phusion Passenger is a fully-featured, mature product that stands on its own, even without Enterprise enhancements. Deliberately making software fail with obscure errors, such as what appears to be the case for BrindleFly, goes against every part of our philosophy and morals. I can assure you that the problems described in this topic have got absolutely nothing to do with us selling a commercial version.
You mentioned "a lot of the same issues on Passenger bugtracker", and "the bug is years old". Can you point out which ones exactly? The described issue bears similarity to some old issues in Phusion Passenger 3 (and indeed, BrindleFly is using version 3). Those issues have been fixed in Phusion Passenger 4, released in May 2013. Even in the open source version. Version 4 is a major improvement and closed many issues on our bug tracker. In the past half year alone we've managed to reduce the number of outstanding issues in our issue tracker by 50%.
You see, in Phusion Passenger 3, the core I/O engine was multithreaded and there were certain I/O patterns (which involve file uploads) that it didn't handle correctly. In version 4, the core I/O engine has been entirely rewritten in an evented manner, not unlike how Nginx itself works. All I/O patterns are now handled correctly.
I would like to invite you, or anybody who experiences similar problems, to contact us through the Phusion Passenger community discussion forum: https://groups.google.com/forum/#!forum/phusion-passenger and to provide more information. If there is a bug, we'll do our best to fix it, Enterprise user or not.
With kind regards,
Hongli Lai