blockchain technology transaction failure?

I took Oleg's advice about a year ago and opened a crypto account with NDAX which has been flawless until now. Note that I am very careful with my cryptocurrency transactions.

On the morning of Tue. Nov.25, 2025, I attempted to send 50k XLM from my Ledger Nano S digital hardware wallet to my NDAX crypto exchange account in 2 separate transactions.

At 10:43 am, I sent 10k XLM which was immediately received okay in my NDAX account at 10:43 am.

At 10:49 am, I sent 40k XLM which was not acknowledged in my NDAX account and they requested all of the details for their investigation which I provided.

This type of failure event has never happened to me before and astonishing since blockchain technology seems to have failed which I did not think could happen in this manner.

I am very interested in any similar situations that anybody knows about or have heard about and please share.

/ B