The authors of Clash of Clans and Clash Royale admitted that they underestimated the competition in the free-play games market and did not work properly with players.

Despite the victory, the course of the battle shows a loss! This can happen if in the middle of the battle you lose your connection to the servers. The battle has already begun, but the connection was lost before you deployed all the troops. Game servers only consider troops deployed before losing a connection. Most clan members, if not all, at least once survived this, and the developers understand how insulting it is.

Before starting an attack, find a good Wi-Fi signal or at least a good 3G / 4G connection. Sometimes all the Wi-Fi or mobile phone bands may not be enough for a permanent connection, as local networks can be overloaded or just slow down. This is especially true if you are traveling in a moving car or underground public transport.