For aviation applications, use of a dedicated GPS receiver is often recommended. While WiFi+Cellular models of iPad incorporate a GNSS receiver within the Cellular chipset - providing accurate position and velocity measurement for a moving iPad - issues can often be encountered within the confines of a GA cabin.
Signal loss can be caused by many contributory factors including signal blocking, multi-path interference and signal jamming (increasingly common in many areas of Europe, the Middle East and some other regions). Electrical/radio devices combined with sub-optimal GNSS antenna location can all combine to cause loss of signal lock. Even a film of water on a surface that covers/shades the iPad can block GNSS signals.
You might be well advised to consider use of an external GNSS receiver or repeater - as this allows the GNSS antenna/receiver to be placed in a better location (e.g. above the combing) with an unobstructed view of the sky. There are external receivers many from which to choose - both wired or wireless (Bluetooth) being available; BadElf have good reputation - as does the GNS1000.
If your iPad has fault, it may require repair. For practical purposes, in lieu of repairing and returning your own iPad, Apple usually exchange the iPad for a renewed/refurbished iPad of the same model and specification. The cost of the exchange is the same as would otherwise be charged for repair. Unless you have benefit of an active AppleCare plan, an out-of-warranty repair while expensive will be somewhat less than the cost of a replacement iPad.
As for out-of-warranty repair costs, Apple offers a fixed-price price repair. You can verify eligibility and cost for your region/country here:
iPad Repair & Service - Apple Support
If you have an active AppleCare+ plan, the cost of repair is reduced to a small excess/deductible fee.