Run ahead second instance : increase times loading games for 20 s

Hi, I use run ahead option each time if possible on cores on android shield tv with roms and chd collection stored on a Nas synology. In order to eliminate lag, I have to add on some cores the 2nd instance run ahead option enable (neo cd, sn9x with msu-1 games, etc …). but this option increase the loading time games for 20 seconds and freeze retroarch during loading. is there any thing to do to eliminate this long process loading time game ? is it a bug or the process whitch is required ? if i disable 2nd instance, games load immediately. thanks for your help.