Differents explorers arent synchronized
The explorers are not synced with each other; they display different blocks. It seems like Dash's testnet has been reset multiple times so chain.so is using one version of the testnet which dash.siampm.com is using a different version of the testnet. This means that they are using different blockchains. Thus your transactions will only appear correctly on the one that is using the testnet chain that you are using.