According to the drawing of the internal logic diagram for 74ALS869, S0 must be 0 in order to activate the 3-inputs NAND, together with ENT# and ENP# for counting up/down mode.
But input S0 is required to be 1 for counting UP/DOWN, as shows the Function Table:
Datasheet is marked as SDAS115C – DECEMBER 1982 – REVISED JANUARY 1995, and it is available at:
https://www.ti.com/lit/gpn/sn74als869
Any comment about?