I am experiencing the exact same problem (Sprint, G5, Lollipop). I've used Titanium backup to uninstall connections optimizer and have all the same settings otherwise. I have tried working with Fabio, but he is still insisting connection optimizer is resetting the WIFI connection, which causes tethering to drop out.
I have used the android app "SysLog" to capture android logs to try and figure out what is going on, but have not found any other applications that could be interfering with the WIFI connection.
Is there someone that might be able to analyze my logs further and create a patch to try and remedy this problem? Please PM me.
Any luck finding culrpit? I also used Titanium backup to freeze Connections Optimizer and it did not solve issue. I also cannot use the ##3283# method to activate hotspot due to all methods to recover MSL that I have seen (like getprop ril.MSL) no longer work on S5 Lollipop.
If anyone also knows how to get MSL code for SM-G900P on Lollipop, please let me know. Yes, I've already tried calling/chatting with SPRINT, but they are on to this method and will not give out MSL anymore.