A 26 point increase from your first LSAT to your last is a pretty significant (and awesome!) increase that will merit a brief, explanatory addendum. But you don't need to take the test again to prove the 172 is legitimate. The LSAT has a lot of security protocols in place and LSAC would have flagged your test if they thought it was suspicious. Law schools are going to want to take your higher score. So just give them an explanation to make it easier for them. The key is to keep this addendum brief and don't make it a list of complaints/excuses as to why your other scores were lower. Use this as an opportunity to subtly showcase your persistence in the face of obstacles, dedication to pursuing law school, and ability to learn and grow (but don't get too flowery--keep it succinct and to the point). Clearly explain why your earlier scores were not reflective of your ability, why you thought you could do better on another test, and how you prepared. Remember that you are explaining a positive (a great LSAT score!) so be careful not to make it into something that sounds negative (e.g., focusing too much on how unprepared you were the first time, overly complaining about tech issues with the Flex, etc.).
A few resources that you may find helpful:
https://blog.powerscore.com/lsat/whats- ... h-addenda/
Hope this helps! Good luck!