I don’t believe we can. A host is is either proxied though Cloudflare or it isn’t. At a DNS level the lookup is done for the DNS host name and the full URL path isn’t passed to a DNS server. As a result the address returned is going to either be our proxy or it isn’t (orange or gray cloud is binary).
There are things we can do in page rules like resolve override to send traffic to a different host, but the traffic itself has to go through Cloudflare for a page rule to fire (and that wouldn’t solve your problem anyway).
So two possible options:
Change the host name for that particular path (e.g. from “http://bboostr.com/generator” to “http://bypass.bboostr.com/generator”) and gray cloud the bypass record.
Determine how/why an error is being generated when accessing that portion of the site. It may be that either the file upload is too large (if it is a file upload) or you could be hitting the http timeout for generation of your file… in which case you may want to modify the code to send a keep-alive message to the client or a notification when the file is complete to then download it.