Hello Vojtech,
Thank you for your question about a snipe. The pattern you describe sounds like you are being outbid by proxy bids.
You can see the error that eBay returned:
1. Go to your Completed tab.
2. Verify snipe placement times listed.
3. Click the "log" icon next to your snipe.
4. Review the full execution history.
If there is an error returned by eBay, it will be shown on the Completed Tab and in the above execution history.
I hope I answered your question to your satisfaction. Please let me know if I can help further.
bidslammer