There's been an attempt lately to disrupt the @monero network through a Sybil attack. @fluffypony explained it very well in this thread:
Riccardo Spagni
 @fluffypony
10 Nov 2020
Recently, a largely incompetent attacker bumbled their way through a Sybil attack against Monero, trying to correlate transactions to the IP address of the node that broadcast it. Whilst novel in that it is the 1st Sybil attack of this sort, it was also quite ineffective. 1/n
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For Monerujo users using random discovered nodes it meant some transactions not being broadcasted, stuck, or returning errors. We encourage them to try troubleshooting them using either your own node or one of the public community-trusted ones.
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Replying to @monerujowallet @monero @fluffypony
For example, adding manually these ones to your favorite nodes: opennode.xmr-tw.org at port 18089 uwillrunanodesoon.moneroworl… at port 18089 node.xmr.to at port 18081

1:00 PM · Nov 10, 2020

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We're also exploring design choices to mitigate this type of annoyances in the future. Your feedback is always useful so don't hesitate to contact us!
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