PyCharm skips keyboard characters when typing

For like a month or more ago there's a problem with delays and skipping of input characters. For example:

• what I do: type "for line in input_lines"
• what I get: written "for line input_lines" - "in" is missing, when typing there's a huge slow down after pressing [space] after writing "line", all input during this time is skipped

That's not the only case, it happens all over in many syntax constructs. This stops happening when I use Power Save Mode.

My suspicion is that code insight / completion has too big databases.

My situation:

• PyCharm - latest
• opened projects: 10 in the same window, with a few interpreters
• Python 3.5
• opened files: for example 3 now and the problem is present
• Linux 4.13.0-41, Ubuntu 17.10
• SSD drive
• RAM: 80% used now, 300-400M "of 725M" is shown in PyCharm window