I attempted to turn on my big w string lights (3 strings from mfc originally) this morning. I had not tested them this year before then. About the first 20 come on, with every 2nd light in the next 10 very faint and then none work until about another 10 at half strength towards the end. I have had a quick look over but can't see any obvious issues. Just hoping someone may have some advice to diagnose the problem. Thanks.