I have been searching for an explanation for Technetium's instability both here and across the net including the "Why is Technetium Unstable" and I haven't found an answer that is satisfying to me. However when researching this I did notice that Molybdenum and Ruthenium both have a high number of stable isotopes (6 and 7).
This is my current mental model of radioactive decay. If you consider all the arrangements of the nuclear particles as existing in a phase space. Then an atomic nucleus sits in a local minima of protentional energy. A stable nucleus is one where the walls of the the potential well are so high it is impossible to get out of.
The Molybdenum and Ruthenium isotopes have very deep potential wells which makes them stable. However because Technetium's close to them in phase space it doesn't take much for technetium to slip over the wall and decay into those other elements.
Is this model flawed? And what impact to the fact that Molybdenum and Ruthenium have on the stability of Technetium.