Adrian on "[Plugin: Jetpack by WordPress.com] Photon loads wrong image proportions"

Problem with wrong thumbnail image proportions occurs on smartphones.
I only have the iPhone 6+, but the problem can be demonstrated to occur on various smartphones by (on a Mac) using the Xcode device simulator, or using Chrome's Developer Tools device mode.
Problem occurs with slider on our homepage at https://comptonshawford-pc.gov.uk/

Some of the thumbnails shown in the slider (on a smartphone) have the wrong dimensions when photon is active.

The html source to display such a thumbnail (if you're using s smartphone) is
Without Photon:

<div class="wpp_image">
<a href="https://comptonshawford-pc.gov.uk/2016/04/local-elections-may-2016/"><img height="110" class="wpp_image_right" src="https://comptonshawford-pc.gov.uk/web/wp-content/uploads/2016/04/ballot-woman-300px-250x254.png" align="right" scale="0"></a>

With Photon

<div class="wpp_image">
<a href="https://comptonshawford-pc.gov.uk/2016/04/local-elections-may-2016/"><img height="110" class="wpp_image_right" src="https://i1.wp.com/comptonshawford-pc.gov.uk/web/wp-content/uploads/2016/04/ballot-woman-300px.png?zoom=3&fit=250%2C254&ssl=1" align="right" width="249" src-orig="https://i1.wp.com/comptonshawford-pc.gov.uk/web/wp-content/uploads/2016/04/ballot-woman-300px.png?fit=250%2C254&ssl=1" scale="3"></a>

You can see that photon modified the src parameter (as expected) and added an src-orig parameter. But it also seems to have added width="249" which is causing the thumbnails to have the wrong proportions.

Photon is currently activated so you should be able to see the effect.

I'm using a chargeable plugin, WP Posts Pro, to display the slider.
It allows me to override the thumbnail height, which I have set to 110.
It's working the way I want when photon is inactive, but obviously I would like to be able to use photon.

Note: I also use a caching plugin which I have temporarily deactivated so that it doesn't interfere with the diagnostic process.