Hard shifting like that is not uncommon for the AX-15 and is often the sign that a synchro is going out.
However, it is fussy about the gear lube you install into it. You can't fill it with just any tranny gear lube and most of the time you can't use GL-5 which is the most commonly found gear lube. Its actual specification is a GL-3 75W-90 gear lube but the newer GL-4 spec 75W-90 like Redline's MT-90 is ideal. GL-4 is an upgrade to GL-3 and it works fine in that transmission.
The confusing thing is where GL-5 (really meant for axles) forms of 75W-90 are concerned. Generally speaking, GL-5 gear lubes should not be used and 99% of the gear lubes you find on the store shelves are GL-5. Most GL-5 gear lubes are harsh on the synchronizers used in the AX-15 (and AX-5 for you 2.5L four-banger owners).
However, there are SOME GL-5 lubes that are ok and those include the synthetic 75W-90 gear lubes like from Royal Purple and Amsoil. They have a different formulation of GL-5 that is not harsh on the synchronizers.
My personal choice for the AX-15 and AX-5 is Redline's MT-90. It is a fully synthetic GL-4 75W-90 and those transmissions really like it. It's not a miracle gear lube and it won't fix damaged transmissions but it can often fix tough shifting issues caused by old or incorrect gear lube.
One last comment... only ATF for automatic transmissions is pink, the correct gear lube used in the AX-15 is decidedly not pink.