Why do I get weird results when using high perpexity in t-SNE?

This mess is likely not due to a property of the algorithm, but due to the implementation you used not catching invalid parameter inputs. Note that the perplexity of a distribution over N items can never be higher then N (in this case, the distribution is uniform). For t-SNE this means you need at least 101 points to be able to use perplexity 100.

https://stats.stackexchange.com/questions/332370/why-do-i-get-weird-results-when-using-high-perpexity-in-t-sne