It's difficult to say why the
Achilles tendonitis/tendinosis continues to reoccur without evaluating your foot, but based on your history it seems likely it is due to a combination of the types of shoes your are wearing and your foot type. Do you have a high arch foot or a low arch foot? If you've been told you have a Haglund's deformity in the past and you are experiencing peroneal brevis tendon problems, then my guess is that you have more of a high arch foot. Or, you have a high arch foot with sitting which is very flexible and collapses with standing. Both foot types are prone to Achilles problems.
Another common issue with chronic Achilles tendonitis/tendinosis is a tight calf muscle. When the calf muscle is tight, it causes excess stress on the Achilles tendon. The heel comes up early when walking, placing excess stress on the arch and the tendons on the inside of the foot (posterior tibial tendon) and outside of the foot (peroneal tendon). This tends to be an underlying
cause for many common foot problems.
Calf stretching, heel lifts and
supportive shoes are the keys to prevention. Crocs are very flexible shoes which offer no support and contribute to many foot problems.
A Haglund's deformity is a bony prominence on the back of the heel which is due to a certain foot type (generally a high arch) in combination with excess rubbing on the heel counter of the shoe. A retrocalcaneal spur, is spurring which develops on the back of the heel in response to excess stress and traction from the Achilles tendon, and can be associated with insertional
Achilles tendonitis.
Lastly, a 14 mm longitudinal intrasubstance tear is not very long and it's hard to know exactly what this finding on the MRI actually represents.