Title and description metatags sometimes not received

Hello,

I have problem with the title, meta keyword and descriptino on some products. My site is https://www.singular-cy.com , and the correct is for example:

<title>SteelSeries World of Cataclysm MMO Gaming Mouse - Mouse - laser - 14 button(s) - wired - USB [62100] - €83,93 : Singular E.Shop, Cyprus, CY, Limassol, Greece, GR, Computers, Graphics Cards, Monitors, Hardware, Printers, Scanners, Mainboards, CPUs, HDD, Hard drive, External, iPhone, iPad, eshop,  - Best Prices</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="keywords" content="SteelSeries World of Cataclysm MMO Gaming Mouse - Mouse - laser - 14 button(s) - wired - USB [62100] Cables Laptops Cooling Graphics Cards Optical Drives Mainboards Memory RAM Processors Computers Consumables POS Products Digital Cameras Monitors Multimedia Networking Phones Print and Scan Blank Discs - Media Controller Cards Mac Projectors UPS Power Supplies PC Hard Drives Input devices Computer Cases Default category Flash Memory Consoles Navigation Software iPhone-iPad Gift Certificates Surge Protectors Random Hot Offers Today " />
<meta name="description" content="Singular E.Shop, Cyprus, CY, Limassol, Greece, GR SteelSeries World of  Cataclysm MMO Gaming Mouse - Mouse - laser - 14 button(s) - wired - USB [62100] - World of Gaming MouseWORLD OF  ®Beautifully crafted, World of themed hardware and user interface.IN-GAME SETUPBind all 15 buttons from within World of for MAC and PC users.CUSTOM MACROSCreate custom macros also supports in-game macro language.ERGONOMIC SHAPEOptimized button layout and ergonomics for comfort, performance and control.ADVANCED ILLUMINATIONChoose from " />

But on some products, while everything else the correct, these things are:

<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="keywords" content=" " />
<meta name="description" content=" " />

Any idea?
Thanks