Archer's Auto Attack and Some Skills Couldn't Connect

So, it all started when I was farming Shell Masks with my guildies, around January. I had always farmed using my archer (not gunner) there, without any problems. I hid other players as usual. But at that time, something funny happened.

Whenever I auto-attacked on the Shell Masks, the attack wouldn't connect. It doesn't have a miss sign on the mob, but it doesn't hit either. Sometimes, even my Power Shot and Snipe got the same problem as well. Then, this keeps happening in every laggy areas, not just in Nisel Mountain.

I have played this game since the start of November 2015. But this problem occured on January 2016, until now. It's weird. I had to use my Dual Wielder a lot, and it sucks. (My DW doesn't have any problem, even in laggy areas).
I tried re-install it a few times, with no avail. I already closed other background apps, but still wouldn't help. I have a security app, which sometimes, causes apps to force close. But after I uninstall it, it still has the same problem. I use a mobile data connection. Using wifi here is even worse. -_- This already happened, before the update to v2.0.0.

Here's the core specs of the phone I'm using to play this game:
Internal: 4GB
RAM: 1 GB
Processor: Qualcomm Snapdragon 400(Quad Core, clocked at 1.2 GHz)
OS: Android KitKat 4.4.2
Is it because of the RAM? I used the same phone, even before the problem happened. I tried to contact Asobimo a few times, but they kept asking about what mob am I having trouble with and what my equipments were. I replied to tell them, that it wasn't about the mobs, nor the equipments, it's about my archer. My DW doesn't have any trouble in laggy areas. Then, they didn't reply...-_-

So, guys. Any of you experienced the same issue? Please let me know.