Very long columns text file become "no response" after v17.6

Sometimes we need to edit very long columns text file, for example > 1,000,000 columns.
But it will become “no response” after v17.6, include v17.6.0 beta 1 (17.5.901).

Reproduce way:
Win 7 64bit, Emeditor v17.6 ~ v18.1 64-bit portable, all default settings.
1. Open a very long columns text file, for example > 1,000,000 columns.
2. Press “End” key, move the cursor to the end of line, for example Ln 1, Col 1,000,000. -> “no response” for a while(several seconds) in v17.6, but, in v18.1 almost hangs or freezes.
3. Click to any col near the end of line, for example click on Ln 1, Col 999,950. -> “no response” for a while (several seconds).
4. Select any text to highlight. -> “no response” for a while (several seconds).

Compared to v17.5
1. Open a very long columns text file, for example > 1,000,000 columns.
2. Press “End” key. -> OK, within 1 second.
3. Click to any col near the end of line, for example click on Ln 1, Col 999,950. -> OK, within 1 second.
4. Select any text to highlight. -> OK, within 1 second.