water softener backing-up

We’ve had an AEG Favorit 40250I-W for about 7 years and for most of that time we haven’t used any salt because the water we have is soft anyway. I’m thinking that was probably a mistake…last week the anti-flood switch tripped the machine and there was half a pint of water underneath. I mopped up and it reset but two washes later it tripped again. I took the side off and could see that the overflow pipe at the bottom of the Regeneration doser was spitting out small amounts each time it filled the Regeneration crystals chamber. It was as if the measure of water couldn’t get in quick enough and the last of it came out of the overflow. In a complete wash cycle it amounted to 300mls. It looks like the crystals are compacted? I’ve put salt in now and turned up the setting for maximum saltiness in the hope it will soften the crystals. Am I on the right path do you think, or barking up the wrong tree?