'95 LX-HatchB Trans slip, no/late 1-2 shift

'95 LX-HatchBack - Low milage (65,000km)

Transmission not shifting or sometimes it is late shifting into 2nd
(late meaning it sometimes shift at over 4000 RPM -
but will shift back into first very quickly)

Fluid & filter changed - (first time that we know of)
it was darkish color, but not black or brown
no burnt smell either.

No ecc codes.

It was a sudden change,
one day it worked fine then the next it didn't.

It has happened once that it shifted fine, but it didn't last long.

Any ideas...Vacuum, Trans soleniods, ???

Thanks in advance.

Glen