At 142k miles on the original trans...... it is way past it's service life expectancy .
The band for 2nd & 4th gear is the same band. The band may be worn and not holding power in 2nd gear. Usually 4th gear is weak too. The servo for 2nd / 4th gear band usually does not fail if it has worked correctly for many miles.
You could have a worn out accumulator for 2nd gear. These accumulator pistons can break or wear out the bores and then leak. This will weaken 2nd gear holding power too.
IF you drop the pan , the 2nd gear accumulator is held on the trans case with 3 bolts... 2 short , one long.