These have a simple three range HST transmission. Three speeds via simple spur gear sets. Rugged but finicky on how they shift. All three models TLB I have bought used, B20, B26 and M59 have had their range lever bent from someone using too much force to change gears instead of taking a little time to allow the gear teeth to align. Even the owners manual says up to 30 seconds which seems like an eternity when working. Does seem like when shifted properly they break in and shift quicker and smoother over time. It is important these gears are fully engaged.
Your first picture shows it should be in neutral. The linkage “C” slots should be aligned with range lever. Linkage is designed to not allow being in two gears at the same time. Which linkage is not in neutral? Can you tell which range your in? The right linkage not engaged with the shift lever might need to move up.
One picture shows a linkage rod jam nut not tight to the adjustment turnbuckle nut. Can’t tell if this is the cause of the problem.