Let me start off by saying that I agree that I think ARB is an exceptionally run company which focuses on delivering quality products. I think that some of the decline is due to the incentives in the market that shift buyers from diesel products towards electric alternates, which may be inadvertently pushing them away from the traditional ARB products.
Here's a look at some of the YOY sales for the typical end users of ARB products, from the top 10 vehicles in Australia:

ARB have pivoted and now have parts available for the BYD Sealion (13,410 vehicles in 2025), so there is a potential for them to claw back some of the drop in volumes for the Ford Ranger over the next year.
There are other factors at play as well (i.e. DMax increasing their base price by 10%/$3,500), which doesn't paint the whole picture. More care sales over the next year will work out if there is starting to be more of a shift towards BYD and other vehicles that do not offer ARB add-ons.
I agree with Rick that the PE is high and the ROE has been reducing over the past few years. I sold my ARB shares in 2023 when the Covid Crazy in the car market started to show signs of dissipating. I am keen to hold this company again at some point, but right now I don't have the confidence to dip my toe in the water again just yet. Will be monitoring the situation to see if this is just a short term blip in their quite successful journey.