I should have phrased my question a little differently...is the site upload functioning at the moment? Timeouts are indicative of an error, especially when the dimensions and file size for the attempted upload (jpg) are well within limits.
For troubleshooting purposes here is what I've experienced:
Macbook Pro 15 running macOS 10.12.6 (Sierra) using Chrome Version 61.0.3163.100 (Official Build) (64-bit)
Steps to reproduce:
1. Start a new thread
2. Click on 'Managed Attachments'
3. Dialog window opens
4. Select 'Browse' and select image from downloads folder (jpeg, 500 x 300, 44K)
5. Click upload
6. 'Waiting for
www.trawlerforum.com' is displayed in the browser footer
7. Timeout error is received in dialog (see below):
This site can’t be reached
www.trawlerforum.com took too long to respond.
Try:
Checking the connection
Checking the proxy and the firewall
ERR_TIMED_OUT