What is the reason why mobile phone messages are always delayed or not displayed?

My mobile phone is LG P350, an Android phone. There are also delays in receiving short messages, and what is even more hateful is that many times people can't receive them directly, especially the letters from the group flying are more serious. Many times, other programs and SMS programs will be forced to shut down.

The SIM card has been replaced and is invalid. It is ok to change your mobile phone.

I searched the internet and found that many mobile phones have this problem. Some solutions are to delete the SMS software that comes with the system and replace it with other SMS software.

I just deleted a few mobile phone bundles that will be forced to shut down after I get ROOT permission (I dare not delete them if I don't know). Then I installed a short message software, and I didn't delete the system itself. It still doesn't work.

So maybe it's something else. I want to ask myself.

This is my problem. I ruled out the delay caused by busy text messages. But yours may also be caused by the busy SMS system.