Missing Assets error message

[laserman]

I have been working on next year's show adding matrices and yard props and suddenly got a new "Missing Assets" error message.  The location of the missing asset is a photo in a file folder I have not used since my first year in 2018. After 2018 I copied the photo to a common pictures folder which I have used the last two years.  The three sequence locations where I use the photo all correctly reference the latest file location and they all work fine.  How do I fix this?  Is there way to see how/where/why X-lights is generating the message?  FYI - I recently updated to the latest version of X-lights after last updating in December but I had used the new version at least a couple of times before I got the error message.
I am hesitant to continue sequencing in case I have to do something major to correct the problem such as use an old backup. 

[laserman]

So I figured out how to find the problem.  Using the Tools/Check Sequence (as suggested by the error message) I was able to pin point the problem picture.  What I will never know is how it suddenly got there.  As mentioned in the first post, the errant picture file came from an old 2017 folder that I haven't used in three years.  I have not added any new pictures, and certainly not in the location in the sequence where I found this random picture.  At any rate - problem solved by deleting the picture from the sequence.