Ok, so that does seem like it’s the self-signed certificate that is causing the issue. You are under no obligation to buy one, but browsers are clamping down on them in an effort to prevent fraud, so for ease, it’s something you ishould consider.
There’s a couple of settings in Sense that may help with the timeout. Main one in this case is in the Virtual Proxy -> Advanced setting. Adjust the Keep Alive timeout setting upwards to 120 or similar. It can help if the connection is slow.