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Ijust installed Ubuntu 18.04.01 LTS in my pc, and every time i press num lock and caps lock, the system freezes a little, taking seconds to get back working. It turns to be very frustrating when i press numlock by accident, and have to press again, freezing again.

My lspci output:

    00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor Family DRAM Controller (rev 09)

    00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)

    00:16.0 Communication controller: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 (rev 04)

    00:1a.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 (rev 05)

    00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 05)

    00:1c.0 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 (rev b5)

    00:1c.1 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 2 (rev b5)

    00:1c.2 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 3 (rev b5)

    00:1d.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 (rev 05)

    00:1f.0 ISA bridge: Intel Corporation HM65 Express Chipset Family LPC Controller (rev 05)

    00:1f.2 IDE interface: Intel Corporation 6 Series/C200 Series Chipset Family 4 port SATA IDE Controller (rev 05)

    00:1f.3 SMBus: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller (rev 05)

    00:1f.5 IDE interface: Intel Corporation 6 Series/C200 Series Chipset Family 2 port SATA IDE Controller (rev 05)

    01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller (rev 05)

    07:00.0 Network controller: Qualcomm Atheros AR9285 Wireless Network Adapter (PCI-Express) (rev 01)

Answer found here:
Fn Media keys slow/delayed on ubuntu gnome 17.04

For some reason my Gnome freezes when using Fn keys, or when I try to use 2 keyboards. A friend of mine pointed to me that it occurs when switching to a keyboard layout that has Scroll Lock enabled, so I disabled it in the X11 keyboard layout file for my language and it solved the problem.

The steps I followed are:

Opened the keyboard layout file for my language, in my case:
sudo nano /usr/share/X11/xkb/symbols/br

Commented the line:

modifier_map Mod3 { Scroll_Lock };

Logged out and logged in again.

These steps are specific for the Brazilian Portuguese ABNT2 Layout and may not work for other layouts, but it can help you find a similar solution.