Just remove the adjustment. There have been some changes to the calendar API (the docs are being rewritten by @Zaidchhapra so expect an update in a few days inshaAllah).
The default calendar is now Umm Al Qura (which does not really need the adjustment). In fact, it should not accept the adjustment but it had just been enabled to test out something and you seem to have hit during this time. I've just disabled it again.
There calendar now supports multiple methods: https://api.aladhan.com/v1/islamicCalendar/methods.
The adjustment parameter will only work if you use the MATHEMATICAL method.
To pass a method, use the calendarMethod query param. So, for instance https://api.aladhan.com/v1/hToGCalendar/7/1446?calendarMethod=MATHEMATICAL&adjustment=2.
There has also been an update where all methods now try and correct the date. The real issue is also going from Hijri to Gregorian (not so much the other way around, except in the mathematical method), so the API tries to compensate for mathematical errors when going backward with any method. You should very rarely need the adjustment parameter going forward. And if you use the HJCoSA method, in principle, you should not need an adjustment at all as long as you are happy with UAQ as the base adjusted for actual lunar sightings.
