Or search: frail, tense, faulty, flawed, corrupt, fallible, blemished, corrupted, defective, irregular, progressive, flawlessness
1 Syllable: S
learned
2 Syllables: SU
Berwick, blurted, Burnet, burnished, earnest, Ernest, furnished, herded, perfect, permit, skirted, surfaced, thirsted, turgid, verdict, worded, worship, worsted
3 Syllables: USU
adverted, alerted, allergic, concerted, converted, deserted, diverted, exerted, inserted, inverted, perverted, reasserted, reverted, subverted
4 Syllables: UUSU
unconverted

Found 34 words across 4 groupings. Skipped 3 excess words of a similar stem.