File not found error

One more thing - could it be concurrency issue? As I do some reading from Storage in the background process.

I'm not sure this is really related to avoiding NULL value, at least it failed for me not only in places where value was NULL. Could you extend your tests to write/read also not NULL values? Could it have any impact if this is watchface?

Again, I can observe the issue with my watchface. It reads from Storage every minute and fails every 2nd/3rd days - so this is not so often. On top of that - as watchface is restarted automatically, it's no longer as visible as in the past.

Maybe using my app (but previous version - which did not implement avoidance of NULL) could help?

This may be a red herring, but FWIW

In some of my cases of File Not Found error on reading a Storage value, it appeared to be a latency issue in that I overcame it by inserting a delay with a timer before reading the value.
I have not encountered the issue recently and hav not needed to implement the timer.

StachUman CharlySanWF 

I've been looking into this File Not Found Error. I've been reading and writing null into storage on a watch face and I have not seen this error. I've had multiple watches running for multiple days with no crashing. Do you have any more info on this? Where you able to fix it in app code, or is this still happening?

You mean - the issue is when I do store 'null' value? and later I do try to read it?

Null has a meaning in my case - especially when I do store arrays (to know that array is not available).

Also - it happens as well when trying to read (yet I'm not sure if value there is NULL or not null)

Hmm....