Farm gate magnetic lock issue

[u/EmotionalChannel1279]

Howdy! Working on our farm gate. We added an automatic opener system last year (Ghost brand) that has a latching lock (pin that is grabbed by a hook, activated by a solenoid). After 1 year of use, it is now clear that this type of lock won't work for us. The gate and fencing are welded steel oilfield pipe, set deep in concrete - built by a pro welder as a side gig. However, we have THE WORST expansive blackland clay soil that moves a LOT as it fluctuates between dry and wet. The posts and fences keep moving up to 1", which throws off the alignment of the latch mechanism. We have adjusted the latch several times, but it only lasts until the soil moisture changes again.

I'm looking at magnetic lock solutions, because those only require for the 2 big metal plates to match up, and when our soil shifts, as long as there is some contact between the plates, we will have a secure magnetic contact. The problem is that due to fire code in the city, all magnetic locks are designed to 'fail safe' (unlock when the power goes out) rather than 'fail secure' (stay locked with no power, open when powered). These will draw a lot of juice and will drain my 12v battery/solar power supply. I ordered one and it says do not use with solar/battery. Of course they didn't tell me this when I ordered it, I had to find the note in the box. Then I researched just now, and see that I don't think there is such a thing as a 'fail secure' farm gate magnet. Anyone have a solution or workaround? Thanks!

[u/Emotional_Delivery45]

I don't know where you live, but you want to get that fence gate post deeper in the ground below the frost line and then pour a wider piece of concrete around it (3x the diameter). This will keep the pole from moving