New Delhi: Smartphone brands are working on removing the 'green-line' fault cropping up on screens after software upgrades through stringent quality controls, advanced display technologies and extended lifetime warranties.The move comes even as the issue, unresolved for nearly four years, has led mobile phone retailers to dissuade customers from purchasing certain brands and models.The green-line issue is a hardware glitch where a vertical green line appears on the display permanently - often after a software update or after prolonged use. The problem affects models across leading brands - Samsung, OnePlus, Vivo, Realme, Xiaomi and Apple.Vivo, Realme, Xiaomi and Apple did not respond to emails seeking comments.115945989Brands are now working with their supply chain to source better quality displays that can withstand the country's extreme weather conditions, indicating that the fault is arising due to environmental factors of high temperature and humidity, industry executives said."We have increased the number of quality control checks in our factories, ensuring the devices can withstand high temperature and humidity that got the circuits to overheat, leading to faults in the display," a top executive at a leading smartphone brand told ET.The executive added that the mobile phone supply chain has now come out with solutions to ensure these issues don't crop up on future models. This includes the use of better adhesives and sealing techniques, as well as improved cooling solutions to keep the phones from overheating.The hardware fault, which some smartphone brands have acknowledged as a quality issue in some of their products, have hurt sales as customers became wary of purchasing phones from these brands. In letters to brands, industry associations representing mobile phone retailers have sought better policies to tackle the ongoing issue.