I also had the same problem. I disabled all other plugins, but it didn’t help.
I am not a skillful coder, but I was able to solve the problem. NOTE: Use at your own risk.
1. Edit file \wp-content\plugins\text-slider\public\class-text-slider.php
2. Line 324 originally:
public function shortcode($attr) {
after modification:
public function shortcode() {
So I just removed variable $attr.
