This paper focuses on application of a technical debt prioritisation technique in telecommunication software managing a fleet of devices for a video surveillance system. Technical debt for this application was gathered, categorised and prioritised according to the Continuous Debt Valuation Approach (CoDVA), previously proposed by the authors. The following research question was posed: Is prioritising technical debt reduction based on CoDVA effective (i.e., executed as per plan, bringing tangible benefits)? The outbreak of COVID-19 pandemic caused unprecedented disturbance to the engineering organisations worldwide, therefore the technical debt identification phase had to be adapted to cope with a switch to forced working-from-home mode. This was achieved by applying the Wisdom of Crowds method, ensuring broad participation of engineers, and providing a fairly complete picture of the accrued technical debt. Nevertheless, the actual technical debt reduction activities did not follow exactly the expected guidelines. The three main causes of this phenomenon were discovered: continuous refactoring approach, sizing of technical debt items, and the broadened scope of refactoring activities. Therefore, as a result of this case study we propose to adopt a specific broadened definition of technical debt and follow a few rules for defining its scope and granularity.