[UPDATE] Problem with 3.0.164 / webp in 3.0.123

[Marco Ro]

Hi, after the update from the 3.0.123 to the 3.0.164 I have some problem: 

The website start to be really slow and the server often go in times out with error 500. The different in performance was about 5/6s of TTFB. 
I try a lot of different things to recover speed and no longer have the error. In the end we went back to the previous version and everything worked better.

On the 3.0.164 version I notice this error that maybe they can help to understand the reason for the problem with the update:
Analyzing the site with the help of the server provider we found that: the index page make a lot of executions, was 38737 in 1 day. This is to very much for the traffic that we have, in the same day our IP is run 23206 call, that look impossible. 
I'm not sure the problem is about those things, I also the server use nginx, maybe could be this.

At moment we will keep using the 3.0.123 version, but I would like to make the upgrade to use the new API.
Someone can help me to understand why the site has become slow?

UPDATE

I tried to load version 3.0.148, but still I notice a slowdown of the site. The TTFB grow from 2.8 to 6.3

Someone know if there is a way to use the webp format for version 3.0.123 as well?