I would like to add some counter intuitive solution that worked for my use.
I have always been streaming with "HyperDeck Low" which streams @12Mbps.
The average speed was around 11Mbps.
In one of the ATEM updates, BMD decided to raise upper limit and now the setting is set to 12Mbps to 20Mbps.
Now the stream speed averages to around 18Mbps.
Along with that issue, I was also using Companion to set streaming key for different worship services.
(I used macro to set it before Companion added that feature).
And I probably had rtmp rather than rtmps url as I probably copied it from YouTube website.
So I'm not sure which one started the issue first but we were having issues with stream left and right.
Mostly of streaming not start and somehow streaming speed setting got messed up and streaming in really low quality.
I've tried different combination of ways to set the streaming settings.
In the end, the only thing that made streaming stable was to use rtmps + "HyperDeck Low".
Although one thing I didn't try was to create a new service like what @caseybea did.
But I'm not sure if I want to risk having problems again.
We have FiOS 150Mbps internet at the location and I've had 3~4 buffering issues prior to when I started to having above issues.
I had ATEM Mini Pro as soon as it was available to buy.
One thing BMD made worse on ATEM Mini Pro was macro.
I can't seem to be able to modify macros created.
With ATEM TVS HD, I can create a macro and then I can modify or even add a new macro on xml file and update it.
But with ATEM Mini Pro, I was able to modify the ones I recorded but not add a new one.
But that was like early on.
Now, if I make any changes to it, update ATEM MP and then save xml again, either nothing was changed or it actually messed up the macro.
I can no longer make granular changes to macro anymore.