You really should consider proper industrial grade source control. See below.
To fix this, you must find a way to get the information you need in order to reason about what the problem is.
What is often happening in these cases is one of the following:
- the code you think is executing is not actually executing at all
- the code is executing far EARLIER or LATER than you think
- the code is executing far LESS OFTEN than you think
- the code is executing far MORE OFTEN than you think
- the code is executing on another GameObject than you think it is
To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.
Doing this should help you answer these types of questions:
- is this code even running? which parts are running? how often does it run? what order does it run in?
- what are the values of the variables involved? Are they initialized? Are the values reasonable?
- are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)
Knowing this information will help you reason about the behavior you are seeing.
You can also put in Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene
You could also just display various important quantities in UI Text elements to watch them change as you play the game.
If you are running a mobile device you can also view the console output. Google for how on your particular mobile target.
Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.
Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:
https://discussions.unity.com/t/839300/3
As for protecting your work, a wise man once said,
“Use source control or you will be really sad sooner or later.” - StarManta on the Unity3D forum boards
Personally I use git (completely outside of Unity) because it is free and there are tons of tutorials out there to help you set it up as well as free places to host your repo (BitBucket, Github, Gitlab, etc.).
You can also push git repositories to other drives: thumb drives, USB drives, network drives, etc., effectively putting a complete copy of the repository there.
As far as configuring Unity to play nice with git, keep this in mind:
https://discussions.unity.com/t/736093/3
Here’s how I use git in one of my games, Jetpack Kurt:
https://discussions.unity.com/t/807568/3
Using fine-grained source control as you work to refine your engineering:
https://discussions.unity.com/t/826718/2
Share/Sharing source code between projects:
https://discussions.unity.com/t/719810/2
Setting up an appropriate .gitignore file for Unity3D:
https://discussions.unity.com/t/834885/5
Generally setting Unity up (includes above .gitignore concepts):
https://thoughtbot.com/blog/how-to-git-with-unity
It is only simple economics that you must expend as much effort into backing it up as you feel the work is worth in the first place.