HTML5 in IE11 Windows 7 versus Windows 10 not playing

[#1]

We are converting our legacy elearning courses from flash to HTML5 and finding that some get stuck  after the first few slides and just spin or they don't load correctly and have other play back issues. I am finding that if users have Windows 10 and IE 11, then there are no play back problems. If they have IE 11 and Windows 7, then there are streaming and playing issues. To work around this, we are installing chrome as it seems to handle the HTML5 better. Anyone have any ideas why this is so and if there are other things we should be doing as we convert to HTML5?

[#2]

We are converting our legacy elearning courses from flash to HTML5 and finding that some get stuck  after the first few slides and just spin or they don't load correctly and have other play back issues. I am finding that if users have Windows 10 and IE 11, then there are no play back problems. If they have IE 11 and Windows 7, then there are streaming and playing issues. To work around this, we are installing chrome as it seems to handle the HTML5 better. Anyone have any ideas why this is so and if there are other things we should be doing as we convert to HTML5?

[#3]

There are many comparisons about HTML support by browsers,, and all show that IE is about the worst browser. In combination with an outdated OS that is probably the explanation. Switch to Edge is you want to keep with MS (probably not possible with Win7) or to Chrome, Firefox.