Seems like the game upgraded - somewhere around early 1.16, portals search range for the 'nearest' portal was drastically reduced - overworld portal used to search for a matching portal in the Nether within 128 blocks range, Nether portal would cover a whooping 1024 blocks to find a matching overworld portal. This is no longer the case - a Nether portal will seek a sphere of 128 blocks of overworld to find a matching portal; an overworld portal still searches a 128 block sphere but truncates it to 3x3 chunks column centered on the chunk with matching coordinates. (Notably, it does not truncate when choosing a place to spawn a portal, which can lead to a mess of spawning portals in certain circumstances.)
Best solution - just build a pair of perfectly linked portals. Find the x,y,z coordinates of the portal in the overworld (using the F3 debug screen), divide x and z by 8, find the location at x/8,y,z/8 in the Nether and build a portal there. It will take you to the overworld portal, but you should now spend at least 15 seconds in the overworld for the overworld portal to "forget" its old link, before re-entering it - or in certain cases (if this fails) even break and re-light it.
You may 'stretch' the match some - e.g. build your Nether side portal at y coordinate of your ice road instead of somewhere at lava level as you'd be prone to with overworld ground level portals, but remember the restrictions - overworld no more than 128 blocks 'off', Nether - within 3x3 chunks (F3+G to display borders) with the matching coords in the center of the 3x3.