What is a Stable Word™?

Question

_{This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles.}

---

If a word conforms to a special rule, I call it a Stable Word™.

Use the following examples below to find the rule.

Stable words™	Non-Stable words™
even	odd
acidic	alkaline
transparent	opaque
uniqueness	repetition
movableness	mobility
concoction	mixture
explode	implode
trademark	protected
Chinese	Japanese
rare	common
cyclic	acyclic
dared	Scandinavianism
Aaronsburg	Canada
alternate	algorithm

And, if you want to analyze, here is a CSV version:

Stable words™,Non-Stable words™
even,odd
acidic,alkaline
transparent,opaque
uniqueness,repetition
movableness,mobility
concoction,mixture
explode,implode
trademark,protected
Chinese,Japanese
rare,common
cyclic,acyclic
dared,Scandinavianism
Aaronsburg,Canada
alternate,algorithm

The puzzle relies on the series' inbuilt assumption, that each word can be tested for whether it is a Stable Word™ without relying on the other words.

These are not the only examples of Stable Words™, many more exist and can be found.

---

Hint #1

Words that have a certain simple property are automatically disqualified from being Stable Words™. There are four such words on the provided list of Non-Stable Words™, and here are three more:
imply, provide, adjust

Hint #2

Don't tackle the whole word at once, rather look at it a few letters at a time.

Answer 1

My thoughts about this:

A Stable Word™ is a word which, when split into groups of two letters, contains at least two groups that start with the same letter, while at the same time it contains no groups that are identical.

Examples of this:
even -> EV-EN
acidic -> AC-ID-IC
transparent -> TR-AN-SP-AR-EN-T
uniqueness -> UN-IQ-UE-NE-SS
movableness -> MO-VA-BL-EN-ES-S
concoction -> CO-NC-OC-TI-ON
explode -> EX-PL-OD-E
trademark -> TR-AD-EM-AR-K
Chinese -> CH-IN-ES-E
rare -> RA-RE
cyclic -> CY-CL-IC
dared -> DA-RE-D
Aaronsburg -> AA-RO-NS-BU-RG
alternate -> AL-TE-RN-AT-E

Some of the Not-Stable Words contain groups with the same starting letters, but in all of these cases those groups are completely identical:
repetition -> RE-PE-TI-TI-ON
Scandinavianism -> SC-AN-DI-NA-VI-AN-IS-M

Lots of the other Not-Stable words contain repeating letters, but none of them have letter groups with the same starting letter, i.e. none of them have repeating letters in odd-numbered positions:
odd -> OD-D
alkaline -> AL-KA-LI-NE
mobility -> MO-BI-LI-TY
protected -> PR-OT-EC-TE-D
Japanese -> JA-PA-NE-SE
common -> CO-MM-ON
acyclic -> AC-YC-LI-C
Canada -> CA-NA-DA

All the other Not-Stable words, as the words imply, provide and adjust, contain no repeating letters at all.

Not sure yet why this property makes these words stable/not-stable...