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Just because you have a dedicated server doesn't mean you have a full link or performance.
The stability of the link between providers depends on the network that the provider uses and how it allocates the link to the server. And very many providers have shared with other hosts.
If the provider is ZAP Hosting https://zap-hosting.com/en/
I looked by the name of the organization, which has an assigned pool of addresses to serve. I see that the provider is 95% known for gaming servers. I have the impression that the high network load is caused by online games and causes a lot of lag and suspension of the link by the load on the link by other hosts.
I recommend to have a server with a provider that has full transit link support with Tier-1 providers i.e. an example provider as to the quality of the price is Hetzner in the Cloud offering. The latest servers if you hit has a connection with speeds up to 20Gbps
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